Solder paste printing apparatus and printing method

ABSTRACT

When solder paste passes through a first gap located between a pressurizing member and a printing mask during solder paste printing, a pressure directed toward the printing mask is applied from the pressurizing member to the solder paste.

TECHNICAL FIELD

The present invention relates to a solder paste printing apparatus andprinting method for printing a solder paste on a surface of acircuit-forming body, for example, a circuit board, which is an objectto be printed.

BACKGROUND ART

Conventionally, a solder paste has mainly been used when soldering anelectronic component such as a chip componention a printed board inmanufacturing an electronic circuit board, and a solder paste printingapparatus is used for printing this solder paste in the desired pattern.As one example of the squeegee head mounted on a conventional solderpaste printing apparatus, a construction as shown in FIG. 13 can beenumerated.

Normally, during a printing operation, a squeegee head 102 reciprocatesfrom the left to the right and from the right to the left in FIG. 13every printed board 5. In this case, a rightward direction printingsqueegee 101 a is used for the rightward direction printing from theleft to the right, and a leftward direction printing squeegee 101 b isused for the opposite leftward direction printing.

The solder paste printing operation on the printed board 5 by theconventional solder paste printing apparatus 100 will be described withreference to FIG. 13 through FIG. 15.

In FIG. 13 through FIG. 15, reference numeral 3 denotes a printing maskthrough which openings 4 of the desired pattern are formed, 5 a printedboard, 6 a land on which a solder paste 7 is to be printed, and 8 asolder resist. The desired pattern of the printing mask 3 means apattern on which the openings 4 are formed in correspondence with the-lands 6 on the printed board 5.

First of all, when performing the rightward direction printing, theprinted board 5 is positioned when the printing mask 3 in layers so thatthe openings 4 and the lands 6 are aligned in position with each other,and thereafter, the rightward direction printing squeegee 101 a is moveddown in a state in which the leftward direction printing squeegee 101 bis moved up, then bringing a squeegee edge portion 103 in contact with asurface 3 a of the printing mask 3 with an appropriate pressure applied.

In this state, by linearly moving the rightward direction printingsqueegee 101 a in the rightward direction, the solder paste 7preparatorily provided on the surface 3 a of the printing mask 3 isgradually filled into the openings 4 of the printing mask 3. Theprinting operation is ended by moving the rightward direction printingsqueegee 101 a to the right end of the printing mask 3 and thereafterseparating the printed board 5 from the printing mask 3.

When performing the leftward direction printing, similarly to therightward direction printing, the printed board 5 is positioned underthe printing mask 3 in layers, and thereafter, the leftward directionprinting squeegee 101 b is moved down with the rightward directionprinting squeegee 101 a oppositely moved up this time, then bringing thesqueegee edge portion 103 in contact. The subsequent operation issimilar to that of the rightward direction printing describedhereinabove.

Thus, by alternately repeating these operations every printed board 5,the solder paste 7 is continuously printed on the lands 6 of eachprinted board 5 via the printing mask 3 as shown in FIG. 16.

According to the printing using the conventional solder paste printingapparatus 100, the printing squeegee 101 a or the printing squeegee 101b is moved in the state in which the squeegee edge portion 103 of theprinting squeegee 101 a or the printing squeegee 101 b is brought incontact with the surface 3 a of the printing mask 3 with the appropriatepressure applied. As is apparent from the above, the conventionalprinting squeegees 101 a and 101 b perform the two operations of ascraping operation for scraping the solder paste 7 off the surface 3 aof the printing mask 3 and a filling operation for filling the solderpaste 7 into the openings 4 of the printing mask 3 by the squeegees ofone type. This will be described with reference to FIG. 14 and FIG. 15.

FIG. 14 and FIG. 15 are enlarged views of a printing squeegee 101 a andothers for the rightward direction printing. First, as shown in FIG. 14,if the rightward direction printing squeegee 101 a is moved down andlinearly moved in the rightward direction so that the edge portion 103comes in contact with the surface 3 a of the printing mask 3, then therightward direction printing squeegee 101 a reaches the solder paste 7supplied to the surface 3 a of the printing mask 3 and moves whilescraping off the paste.

By this scraping operation, the solder paste 7 flows with a rotationalmotion called the rolling as indicated by arrow I in FIG. 15. At thistime, a fluid pressure is generated inside the solder paste 7.

When the rightward direction printing squeegee 101 a moves further tothe right in the above-mentioned state and reaches the openings 4 of theprinting mask 3, the solder paste 7 is pushed into the openings 4 by theabove-mentioned fluid pressure, and the so-called filling of the solderpaste 7 is achieved. Hereinafter, the pressure by which the solder paste7 is pushed into the openings 4 will be referred to as a fillingpressure.

On the other hand, from the point of view of an improvement inproductivity, it is desired to reduce the printing time even in thesolder paste printing process. However, if the travel speed (squeegeespeed) of the squeegee 101 a is increased in the conventional solderpaste printing apparatus 100 for the reduction of the abovementionedtime, the so-called unfilled portion 9, where the amount of the solderpaste 7 filled into the openings 4 of the printing mask 3 becomesinsufficient, is generated as shown in FIG. 17, causing defectiveprinting. As shown in FIG. 18, there occurs lacks of the solder paste 7printed on the lands 6 of the printed board 5, and stable printingcannot be performed. The reasons are as follows.

If the squeegee speed is increased, then the time during which the edgeportion 103 of the printing squeegee 101 a passes over the openings 4becomes reduced. Therefore, the time during which the solder paste 7 isfilled into the openings 4 (hereinafter, referred to as a filling time)is, of course, reduced.

In order to examine this phenomenon, as shown in FIG. 17, there wasmeasured the filling pressure when a pressure sensor 51 was arranged onthe back surface of the printing mask 3 provided with an opening 4 alocated in the corresponding portion of the mask and the squeegee 101 awas moved at a travel speed of 40 mm/sec and 200 mm/sec. FIG. 19 is agraph showing the measurement results.

The time t along the horizontal axis is the time during which thesqueegee 101 a passes over the pressure sensor 51, and the fillingpressure P is the pressure that the pressure sensor 51 has detected viathe solder paste 7 when the squeegee 101 a passes over the pressuresensor 51.

By this graph, it is clearly understood that the filling time is reducedwhen the travel speed of the squeegee 101 a is increased.

Moreover, although the filling pressure increases itself when thesqueegee speed is increased, the time during which the edge portion 103of the squeegee passes over the openings 4 is reduced, and further theduration of the high pressure is short. Therefore, a sufficient fillingtime cannot be obtained. As a result, the unfilled portion 9 isdisadvantageously generated.

As described above, the conventional solder paste printing apparatus hasnot been able to achieve both of an increase in the printing speed andstable printing.

The object of the present invention is to solve the aforementionedconventional issues and provide a solder paste printing apparatus andprinting method capable of performing stable printing even when theprinting time is reduced for an increase in speed and consequentlyachieving high-quality solder paste printing with high productivity.

DISCLOSURE OF INVENTION

In order to achieve the aforementioned object, the present invention isconstructed as follows.

According to a first aspect of the present invention, there is provideda solder paste printing apparatus for printing a solder paste suppliedonto a surface of a printing mask where an opening is formed by moving asqueegee on the surface in a printing direction on a circuit-formingbody placed on a back surface of the printing mask via the opening, thedevice comprising:

an elongated pressurizing member that has an axial direction extendedroughly parallel to an axial direction of the squeegee and is able toform between the pressurizing member and the printing mask a first gapthrough which the solder paste can pass in a direction opposite to theprinting direction of the squeegee during solder paste printing and isarranged so as to form between the pressurizing member and the squeegeea second gap through which the solder paste can pass from the first gaptoward the squeegee side, the pressurizing member being provided in avicinity of an edge of the squeegee, whereby a pressure toward theprinting mask is applied to the solder paste by the pressurizing memberwhen the solder paste passes through the first gap located between thepressurizing member and the printing mask during the solder pasteprinting.

According to a second aspect of the present invention, there is provideda solder paste printing apparatus as defined in the first aspect,wherein the pressurizing member is movably mounted with respect to thesqueegee between a pressurizing position where the pressure is appliedto the solder paste and a retreated position where the applying of thepressure is released, provided with an axial direction extended roughlyparallel to the axial direction of the squeegee in the pressurizingposition, is able to form the first gap through which the solder pastecan pass in the direction opposite to the printing direction of thesqueegee during the solder paste printing, and is arranged so that thesecond gap through which the solder paste can pass from the first gaptoward the squeegee side is arranged between the pressurizing member andthe squeegee.

According to a third aspect of the present invention, there is provideda solder paste printing apparatus as defined in the first aspect,wherein the pressurizing member is a round bar.

According to a fourth aspect of the present invention, there is provideda solder paste printing apparatus as defined in the first aspect,wherein the pressurizing member has a built-in heat-generating elementfor heating the solder paste.

According to a fifth aspect of the present invention, there is provideda solder paste printing apparatus as defined in the first aspect,wherein a pair of squeegees are provided, and at least one of the pairof squeegees is consistently brought in contact with the printing maskat least during printing.

According to a sixth aspect of the present invention, there is provideda solder paste printing apparatus as defined in any one of the firstthrough fifth aspects, wherein the first gap has a roughly wedge-shapedcross-section shape that is narrowed toward the squeegee.

According to a seventh aspect of the present invention, there isprovided a solder paste printing apparatus as defined in any one of thefirst through fifth aspects, wherein the pressurizing member has aheight from the surface of the printing mask, the height being lowerthan a rolling height of the solder paste during printing, and thepressurizing member sinks in the rolling solder paste during theprinting.

According to an eighth aspect of the present invention, there isprovided a solder paste printing apparatus as defined in any one of thefirst through fifth aspects, wherein the pressurizing member is fixed soas to be unable to rotate.

According to a ninth aspect of the present invention, there is provideda solder paste printing apparatus as defined in any one of the firstthrough fifth aspects, wherein a cross-section shape perpendicular tothe axial direction of the pressurizing member is varied in the axialdirection of the pressurizing member according to a number and a size ofthe openings of the printing mask, thus varying the pressure to beapplied from the pressurizing member to the solder paste against theprinting mask.

According to a tenth aspect of the present invention, there is provideda solder paste printing apparatus as defined in any one of the firstthrough fifth aspects, wherein the pressurizing member is rotated in adirection reverse to a rolling direction of the solder paste around thepressurizing member during printing.

According to an 11th aspect of the present invention, there is provideda solder paste printing method for printing a solder paste located on asurface of a printing mask where an opening is formed by moving asqueegee on the surface in a printing direction on a circuit-formingbody placed on a back surface of the printing mask via the opening, themethod comprising:

applying a pressure toward the printing mask from the pressurizingmember to the solder paste by making the solder paste pass in adirection opposite to the printing direction of the squeegee through afirst gap formed between the printing mask and the pressurizing memberduring solder paste printing in a state in which an elongatedpressurizing member provided in a vicinity of an edge of the squeegee ispositioned in a pressurizing position where a pressure is applied to thesolder paste from a retreated position where no pressure is appliedthereto; and making the solder paste pass again through the first gaplocated between the pressurizing member and the printing mask after thesolder paste that is passing from the first gap toward the squeegee sidepasses through a second gap located between the squeegee and thepressurizing member.

According to another aspect of the present invention, there is provideda solder paste printing method of the 11th aspect, wherein thepressurizing member is a round bar.

According to another aspect of the present invention, there is provideda solder paste printing method of the 11th aspect, wherein thepressurizing member has a built-in heat-generating element for heatingthe solder paste.

According to another aspect of the present invention, there is provideda solder paste printing method of the 11th aspect, wherein, when a pairof squeegees are provided, at least one squeegee of the pair ofsqueegees is consistently put in contact with the printing mask at leastduring printing.

According to another aspect of the present invention, there is provideda solder paste printing method of the 11th aspect, wherein the first gaphas a wedge-like cross-section shape that narrows as the gap approachesthe squeegee.

According to a 12th aspect of the present invention, there is provided asolder paste printing method as defined in the 11th aspect, wherein aninterval of the first gap is smaller than a rolling height of the solderpaste during printing, and the pressurizing member sinks in the rollingsolder paste during printing.

According to a 13th aspect of the present invention, there is provided asolder paste printing method as defined in the 11th aspect, wherein thepressurizing member is fixed so as to be unable to rotate.

According to a 14th aspect of the present invention, there is provided asolder paste printing method as defined in the 11th aspect, wherein across-section shape perpendicular to the axial direction of thepressurizing member is varied in the axial direction of the pressurizingmember according to a number and a size of the openings of the printingmask, thus varying the pressure to be applied from the pressurizingmember to the solder paste against the printing mask.

According to a 15th aspect of the present invention, there is provided asolder paste printing method as defined in the 11th aspect, wherein thepressurizing member is rotated in a direction reverse to a rollingdirection of the solder paste around the pressurizing member duringprinting.

According to a 16th aspect of the present invention, there is provided asolder paste printing apparatus as defined in the first aspect, furthercomprising:

a pressure sensor that is provided within a range of printing on theback surface of the printing mask, which is a range in which thesqueegee moves and detects a pressure of the solder paste applied via apressure detection opening formed on the printing mask; and

a control means for controlling driving conditions of the squeegee incorrespondence with a detection result of the pressure sensor.

According to a 17th aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, whereinthe control means executes control on a basis of a pressure waveformthat represents a change with a lapse of time of the pressure of thesolder paste detected by the pressure sensor.

According to an 18th aspect of the present invention, there is provideda solder paste printing apparatus as defined in the 16th aspect, whereinthe control means is provided with a database in which a pressurewaveform of the solder paste is registered and controls the drivingconditions of the squeegee by comparing the pressure waveform detectedby the pressure sensor with the solder paste pressure waveform that isregistered in the database and becomes a criterion of decision.

According to a 19th aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, wherein asqueegee up-and-down drive device for changing a relative position inthe vertical direction of the squeegee with respect to the printing maskis provided, and the relative position is adjusted by driving thesqueegee up-and-down drive device by the control means.

According to a 20th aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, wherein aprinting drive device for moving the squeegee in the printing directionis provided, and a travel speed in the printing direction of thesqueegee is adjusted by driving the printing drive device by the controlmeans.

According to a 21st aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, wherein apressurizing member horizontal movement mechanism for changing arelative position of the pressurizing member with respect to thesqueegee is provided, and the relative position of the pressurizingmember is adjusted by driving the pressurizing member horizontalmovement mechanism by the control means.

According to a 22nd aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, wherein apressurizing member vertical movement mechanism for changing a relativeposition of the pressurizing member with respect to the printing mask isprovided, and the relative position of the pressurizing member isadjusted by driving the pressurizing member vertical movement mechanismby the control means.

According to a 23rd aspect of the present invention, there is provided asolder paste printing apparatus as defined in the 16th aspect, whereinthe pressure sensor is provided short of a printing start end of thecircuit-forming body, and the pressure detection of the solder paste isperformed before starting the printing of the circuit-forming body.

According to a 24th aspect of the present invention, there is provided asolder paste printing method as defined in the 11th aspect, wherein thepressure of the solder paste flowing between the pressurizing member andthe printing mask is increased by the pressurizing member provided in avicinity of the edge portion of the squeegee, and the driving conditionsof the squeegee are controlled by detecting the increased pressure ofthe solder paste and comparing the detected pressure with a specifiedpressure preparatorily registered.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the control isexecuted on a basis of a pressure waveform that represents a change withthe lapse of time of the solder paste pressure detected by the pressuresensor.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the drivingconditions of the squeegee are controlled by comparing the pressurewaveform detected by the pressure sensor with the pressure waveform ofthe solder paste, which becomes a criterion of decision.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the relative positionis adjusted by changing the up-and-down direction relative position ofthe squeegee with respect to the printing mask.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the travel speed inthe printing direction of the squeegee is adjusted.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the relative positionof the pressurizing member is adjusted by changing the relative positionof the pressurizing member with respect to the squeegee.

According to another aspect of the present invention, there is provideda solder paste printing method of the 24th aspect, wherein, when thedriving conditions of the squeegee are controlled, the relative positionof the pressurizing member is adjusted by changing the relative positionof the pressurizing member with respect to the printing mask.

According to a 25th aspect of the present invention, there is provided asolder paste printing method as defined in the 24th aspect, wherein thepressure of the solder paste is measured before starting patternprinting of the circuit-forming body, and the control of the drivingconditions of the squeegee is completed before starting the patternprinting.

According to a 26th aspect of the present invention, there is provided ascreen printing method for printing a printing paste on a boardsupported by a support base via a screen supported by a screen tablesection by means of a printing head section, comprising:

positioning the board on the support base in a specified position bysupporting and positioning the board on the support base with thesupport base with the board loaded moved up and down with respect to amovable frame capable of moved up and down with respect to the tablesection, moving up the movable frame with respect to the table sectionroughly in synchronization with these operations, and horizontallymoving the table section in a direction roughly perpendicular to a boardloading and unloading direction;

making the recognition camera recognize a reference position markpreparatorily given to the board in accordance with a horizontalmovement of the recognition camera in the board loading and unloadingdirection and a horizontal movement of the table section in a directionroughly perpendicular to the board loading and unloading direction; and

performing relative positional alignment of the board with the screen byhorizontally moving the table section in a direction roughlyperpendicular to the board loading and unloading direction on a basis ofa position of the reference position mark recognized by the recognitioncamera, moving the screen table section that supports the screen in theboard loading and unloading direction, and rotating the screen tablesection within a horizontal plane roughly parallel to the board on thesupport base.

According to a 27th aspect of the present invention, there is provided ascreen printing method as defined in the 26th aspect, wherein the boardon which the printing paste is not printed is loaded in the boardloading and unloading direction onto the support base supportedvertically movably by the movable frame vertically movable with respectto the table section, and the board on which the printing paste hasalready been printed is unloaded in the board loading and unloadingdirection roughly in synchronization with the board loading operation.

According to a 28th aspect of the present invention, there is provided ascreen printing method as defined in the 26th or 27th aspect, whereinthe recognition camera further recognizes the reference position markpreparatorily given to the screen in accordance with the horizontalmovement of the recognition camera in the board loading and unloadingdirection and in the direction roughly perpendicular to the boardloading and unloading direction.

According to a 29th aspect of the present invention, there is provided ascreen printing apparatus for printing a printing paste on a boardsupported by a support base via a screen supported by a screen tablesection by means of a printing head section, comprising:

the screen table section that, is horizontally movably supported by adevice frame;

a table section horizontal movement device for horizontally moving thetable section in the direction roughly perpendicular to the boardloading and unloading direction;

a movable frame that is vertically movably supported by the tablesection;

the support base vertically movably supported by the movable frame;

a screen table section that is arranged above the support base andsupports the screen;

a printing head section that is arranged above the screen table sectionand prints the printing paste on the board via the screen supported bythe screen table section;

a board loading device that loads the board, on which the printing pasteis not printed, onto the support base in the board loading and unloadingdirection;

a board unloading device that unloads the board, on which the printingpaste has already been printed, on the support base in the board loadingand unloading direction;

a movable frame elevation device that is provided in the table sectionand moves up and down the movable frame with respect to the tablesection;

a support base elevation device that is provided on the movable frameand moves up and down the support base with respect to the movableframe;

a board regulation device that positions the board on the support base;

a screen table section horizontal movement device that horizontallymoves the screen table section in the board loading and unloadingdirection;

a screen table section rotation device that rotates the screen tablesection in the horizontal plane roughly parallel to the board supportedon the support base;

a recognition camera that is provided horizontally movably in the boardloading and unloading direction and in the direction roughlyperpendicular to the board loading and unloading direction and is ableto recognize the reference position marks preparatorily given to theboard and the screen; and

a control means for controlling said devices and the recognition camera,

the control means executing roughly in synchronism the loading of theboard onto the support base by the board loading device and theunloading of the board from the support base by the board unloadingdevice in the board loading and unloading direction,

the control means executing roughly in synchronism the support of theboard on the support base in accordance with the elevating operation ofthe support base by the support base elevation device, positioning ofthe board on the support base by the board regulation device, upwardmovement of the movable frame by the movable frame elevation device,horizontal movement of the table section in the direction roughlyperpendicular to the board loading and unloading direction by the tablesection horizontal movement device, and positioning of the board to aspecified position where the reference position mark recognition isperformed by the recognition camera in accordance with the upwardmovement of the movable frame and the horizontal movement of the tablesection, and

the control means executing the relative positional alignment of theboard with the screen by controlling roughly in synchronism the tablesection horizontal movement device, the screen table section horizontalmovement device, and the screen table section rotation device on a basisof the positions of the respective reference position marks of the boardand the screen recognized by the recognition camera.

According to a 30th aspect of the present invention, there is provided ascreen printing apparatus as defined in the 29th aspect, wherein thesupport base is vertically movably supported on a guide shaft fixed tothe movable frame,

the support base elevation device has on the movable frame a ball threadmechanism constructed of a ball thread shaft that has an outerperipheral surface on which a ball thread is formed and a ball threadnut that is provided on the support base and meshed with the ball threadshaft and a support base elevation motor that rotates the ball threadshaft of the ball thread mechanism, and

the movable frame elevation device further has in the table section aball thread mechanism constructed of a ball thread shaft commonly usedfor the support base elevation device and a ball thread nut that ismeshed with the ball thread shaft and rotatably supported by the tablesection and a movable frame elevation motor that rotates the ball threadnut of the ball thread mechanism.

According to a 31st aspect of the present invention, there is provided ascreen printing apparatus as defined in the 29th or 30th aspect,comprising:

a board stopper that is provided on the support base while being able toadvance and retreat and stops the board in a specified position on thesupport base by being engaged with a fore end portion of the boardloaded onto the support base by the board loading device; and

a board detection sensor that is provided for the board stopper anddetects presence or absence of a board on the support base,

the control means controlling the board loading device and the boardunloading device on a basis of a board detection signal from the boarddetection sensor.

According to a 32nd aspect of the present invention, there is provided ascreen printing apparatus as defined in the 31st aspect, wherein acushioning member is provided on an engagement surface that belongs tothe board stopper and is engaged with the board.

According to a 33rd aspect of the present invention, there is provided aprinting screen cleaning method for cleaning a printing screen bysliding a wiping member on a lower surface of the printing screen forsupplying a printing paste onto a circuit-forming body through aprinting paste supply section of a specified pattern with the wipingmember backed up by a backup member so as to wipe the printing pastestuck to the lower surface and sucking the paste via the wiping memberthrough a suction port provided through the backup member, whereby theprinting paste that is stuck to the lower surface of the printing screenor staying in the printing paste supply section is stuck by suction tothe wiping member side and kept by the wiping member,

the cleaning being performed by sliding the wiping member on theprinting screen in a state in which the backup of the wiping member ispartially released by a groove located in the sliding direction withrespect to the suction port of the backup member.

According to a 34th aspect of the present invention, there is provided aprinting screen cleaning device for supplying a printing paste onto acircuit-forming body through a printing paste supply section of aspecified pattern, comprising:

a cleaning head that sucks the paste via a wiping member while slidingthe wiping member on a lower surface of a printing-screen with thewiping member backed up by a backup member through a suction portprovided on a backup surface for performing the backup,

the backup member having on the backup surface a groove that partiallyreleases the backup of the wiping member in the sliding direction withrespect to the suction port.

According to a 35th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 34th aspect, whereinthe suction port is provided in a suction region extended in a directionroughly perpendicular to the sliding direction on the backup surface ofthe backup member, and a groove that is parallel to the suction regionand partially releases the backup of the wiping member is provided.

According to a 36th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 34th aspect,comprising: an elevation device that pressurizes the backup memberagainst the printing screen on the cleaning head or releases thepressurization; and a movement device that makes the cleaning headadvance under the printing screen from a standby position beside theprinting screen and retreat from the screen and move under the printingscreen.

According to a 37th aspect of the present invention, there is provided aprinting screen cleaning device as defined in any one of the 34ththrough 36th aspects, comprising: a supply section that feeds andsupplies the wiping member; and a winding section that winds up thewiping member.

According to a 38th aspect of the present invention, there is provided aprinting screen cleaning device as defined in any one of the 34ththrough 36th aspects, wherein the suction ports are arranged in an arrayin a direction inclined in the sliding direction.

According to a 39th aspect of the present invention, there is provided awiping member backup member comprising: a backup surface for sliding awiping member on a printing screen while backing up the wiping member; asuction region provided in a direction roughly perpendicular to thesliding direction with a suction port provided on the backup surface;and a groove extended parallel to the suction region.

According to another aspect of the present invention, there is provideda wiping member backup member provided with a backup surface forbringing the wiping member in sliding contact with the printing screenwhile backing up the wiping member, a suction region that has a suctionport on this backup surface and is provided in a direction roughlyperpendicular to the sliding direction, and one or a plurality ofgrooves that are parallel to the suction region and provided on one sideof this suction region.

According to another aspect of the present invention, there is provideda wiping member backup member provided with a backup surface forbringing the wiping member in sliding contact with the printing screenwhile backing up the wiping member, a suction region that has a suctionport on this backup surface and is provided in a direction roughlyperpendicular to the sliding direction, and one or a plurality ofgrooves that are parallel to the suction region and provided on bothsides of this suction region.

According to another aspect of the present invention, there is provideda wiping member backup member provided with a backup surface forbringing the wiping member in sliding contact with the printing screenwhile backing up the wiping member, two suction regions that have asuction port on this backup surface and are provided in a directionroughly perpendicular to the sliding direction, and one or a pluralityof grooves that are parallel to the suction region and provided on bothsides of the portion where these two suction regions are arranged sideby side.

According to another aspect of the present invention, there is provideda wiping member backup member provided with a backup surface forbringing the wiping member in sliding contact with the printing screenwhile backing up the wiping member, two suction regions that have asuction port on this backup surface and are provided in a directionroughly perpendicular to the sliding direction, and one or a pluralityof grooves that are parallel to the suction region and provided inpositions provided adjacently on both sides of the portion where thesetwo suction regions are arranged side by side and between these twosuction regions.

According to another aspect of the present invention, there is provideda wiping member backup member of the 39th aspect or any aspectsubsequently described, wherein the suction ports are provided in anarray in a direction inclined with respect to the sliding direction.

According to a 40th aspect of the present invention, there is provided aprinting screen cleaning method for cleaning a printing screen bysliding a wiping member on a lower surface of the printing screen forsupplying a printing paste onto a circuit-forming body through aprinting paste supply section of a specified pattern with the wipingmember backed up by a backup member so as to wipe the printing pastestuck to the lower surface and sucking the paste via the wiping memberthrough suction ports provided through the backup member, whereby theprinting paste that is stuck to the lower surface of the printing screenor staying in the printing paste supply section is stuck by suction to awiping member side and kept by the wiping member,

the cleaning being performed by continuously sucking by the suctionports arranged side by side in a sliding direction.

According to a 41st aspect of the present invention, there is provided aprinting screen cleaning device for supplying a printing paste onto acircuit-forming body through a printing paste supply section of aspecified pattern, comprising:

a cleaning head that sucks the paste via a wiping member while slidingthe wiping member on a lower surface of a printing screen with thewiping member backed up by a backup member through a suction portprovided on a backup surface for performing the backup, wherein

-   -   a plurality of suction ports are arranged side by side in a        sliding direction on the backup surface, and suction is        continuously performed by the plurality of suction ports.

According to a 42nd aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st aspect, whereinthe plurality of suction ports are provided in a suction region extendedin a direction roughly perpendicular to the sliding direction on thebackup surface of the backup member, arranged parallel to the suctionregion and have suction areas reduced stepwise.

According to a 43rd aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st or 42nd aspect,wherein the plurality of suction ports are arranged in proximity to eachother.

According to a 44th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st or 42nd aspect,wherein the plurality of suction ports are provided laterallysymmetrically in the sliding direction.

According to a 45th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st or 42nd aspect,comprising: an elevation device that pressurizes the backup memberagainst the printing screen on the cleaning head or releases thepressurization; and a movement device that makes the cleaning headadvance under the printing screen from a standby position beside theprinting screen and retreat from the screen and move under the printingscreen.

According to a 46th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st or 42nd aspect,comprising: a supply section that feeds and supplies the wiping member;and a winding section that winds up the wiping member.

According to a 47th aspect of the present invention, there is provided aprinting screen cleaning device as defined in the 41st or 42nd aspect,wherein the suction ports are arranged in an array in a directioninclined in the sliding direction.

According to a 48th aspect of the present invention, there is provided awiping member backup member comprising: a backup surface for sliding awiping member on a printing screen while backing up the wiping member;and a suction region provided in a direction roughly perpendicular tothe sliding direction with a suction port provided on the backupsurface, the suction port being comprised of a plurality of suctionports, which are arranged parallel to the suction region and side byside in the sliding direction.

According to another aspect of the present invention, there is provideda wiping member backup member of the 48th aspect, wherein the pluralityof suction ports have suction port areas that reduce in succession inthe sliding direction.

According to another aspect of the present invention, there is provideda wiping member backup member of the 48th aspect or any aspectsubsequently described, wherein the plurality of suction ports arearranged in proximity to each other.

According to another aspect of the present invention, there is provideda wiping member backup member of the 48th aspect or any aspectsubsequently described, wherein the plurality of suction ports areprovided laterally symmetrically in the sliding direction.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a structural view of a solder paste printing apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a structural view of the pressurizing member mounted on thesolder paste printing apparatus of. FIG. 1;

FIG. 3 is a schematic view showing a relation between the pressurizingmember and the squeegee of the solder paste printing apparatus of FIG. 1(note that the hatching of the squeegee 12 a in FIG. 3 is provided so asnot to show the cross-section but to clearly show the region of thesqueegee 12 a);

FIG. 4 is a view showing a rolling state of the solder paste of thesolder paste printing apparatus of FIG. 1;

FIG. 5 is a graph showing the characteristics of the filling pressuresof a squeegee provided with the pressurizing member of the solder pasteprinting apparatus of FIG. 1 and a squeegee provided with nopressurizing member;

FIG. 6 is a view showing a modification example of the pressurizingmember and the narrow path of the solder paste printing apparatus ofFIG. 1;

FIG. 7 is a view showing another modification example of thepressurizing member and the narrow path of the solder paste printingapparatus of FIG. 1;

FIG. 8 is a view showing another modification example of thepressurizing member of the solder paste printing apparatus of FIG. 1;

FIG. 9 is a flowchart showing the operations of the solder pasteprinting apparatus shown in FIG. 1;

FIG. 10 is a structural view of a solder paste printing apparatusaccording to a second embodiment of the present invention;

FIG. 11 is a graph showing the results of a working example 1;

FIG. 12 is a graph showing the results of a working example 2;

FIG. 13 is a structural view of a conventional solder paste printingapparatus;

FIG. 14 is a view showing a state in which printing is performed by thesqueegee shown in FIG. 12;

FIG. 15 is a view showing a state in which the solder paste is graduallyfilled into the openings by the squeegee shown in FIG. 12;

FIG. 16 is an explanatory view showing the solder paste formed on thelands of a printed board after the printing of the solder paste of FIG.15;

FIG. 17 is a view showing a case where unfilled portions of the solderpaste occur in the openings of a printing mask;

FIG. 18 is an explanatory view showing the solder paste formed on thelands of a printed board after the printing of the solder paste of FIG.17;

FIG. 19 is a graph showing a change in a filling pressure relative to asqueegee-passing time by a conventional apparatus;

FIG. 20 is a partially enlarged view of a solder paste printingapparatus according to a third embodiment of the present invention;

FIG. 21 is a schematic view showing a relation between the pressurizingmember and the squeegee of the solder paste printing apparatus of thethird embodiment (note that the hatching of the squeegee 12 a in FIG. 21is provided so as not to show the cross-section but to clearly show theregion of the squeegee 12 a);

FIG. 22 is a view showing the rolling state of the solder paste of thesolder paste printing apparatus of the third embodiment;

FIG. 23 is a graph showing the characteristics of the filling pressuresof a squeegee provided with the pressurizing member of the solder pasteprinting apparatus of the third embodiment, a squeegee provided with thepressurizing member of the solder paste printing apparatus of the firstembodiment, and a squeegee provided with no pressurizing member;

FIG. 24 is an enlarged side view of a state in which the pressurizingmember of a solder paste printing apparatus according to a fourthembodiment of the present invention is positioned in a pressurizingposition;

FIG. 25 is an enlarged side view of a state in which the pressurizingmember of the solder paste printing apparatus of the fourth embodimentis retreated in a retreated position;

FIG. 26A and FIG. 26B are an explanatory view showing a state in whichthe solder paste is protruded from both sides of the squeegee throughthe repetition of the conventional solder paste printing and anexplanatory view showing a state in which the solder paste is notprotruded from both sides of the squeegee through the repetition of thesolder paste printing of the first and second embodiments;

FIG. 26C is a schematic view showing a relation between the pressurizingmember and the squeegee of a solder paste printing apparatus accordingto a modification example of the first embodiment of the presentinvention (note that the hatching of the squeegee 12 a in FIG. 26C isprovided so as not to show the cross-section but to clearly show theregion of the squeegee 12 a);

FIG. 27 is an explanatory view showing a relation of arrangementdimensions of a pressurizing member of a round bar;

FIG. 28A and FIG. 28B are an explanatory view showing a relation betweena board and the printing direction and a graph showing a fillingpressure profile of a relation between the filling pressure and timewhen the printing speed is changed in nine steps from 40 mm/sec to 400mm/sec with no pressurizing member provided for the squeegee;

FIG. 29 is a graph showing a filling pressure profile of the relationbetween the filling pressure and time when the printing speed is changedin nine steps from 40 mm/sec to 400 mm/sec with a pressurizing member ofa round bar provided for the squeegee;

FIG. 30 is an explanatory view showing a relation between the type(viscosity) of the solder paste and a printing condition when nopressurizing member is provided for the squeegee;

FIG. 31 is an explanatory view showing a relation of the type(viscosity) of the solder paste to printing conditions when apressurizing member of a round bar is provided for the squeegee;

FIG. 32 is an overall perspective view showing a solder paste printingmachine on which the solder paste printing apparatus according to afifth embodiment of the present invention is mounted, with a partthereof removed;

FIG. 33 is a perspective view showing the construction of a tablesection 1B of the solder paste printing apparatus of the fifthembodiment;

FIG. 34 is a schematic structural view of the table section 1B of FIG.33;

FIG. 35 is a perspective view showing the construction of a printingsection;

FIG. 36 is an enlarged side view showing the construction of theprinting section shown in FIG. 35;

FIG. 37 is a sectional side view showing the construction of thepressurizing member shown in FIG. 36 with a part thereof removed (notethat the hatching of the squeegee 12 a in FIG. 37 is provided so as notto show the cross-section but to clearly show the region of the squeegee12 a) ;

FIG. 38A is a graph showing the rolling state of the solder paste;

FIG. 38B is a graph showing a time variation in the solder paste fillingpressure detected by the pressure sensor;

FIG. 39 is a control block chart for controlling the squeegee drivingconditions of the solder paste printing apparatus;

FIG. 40 is a flowchart for explaining one control example of controllingthe squeegee driving conditions;

FIG. 41 is a flowchart for explaining another control example ofcontrolling the squeegee driving conditions;

FIG. 42 is a schematic plan view showing a screen printing apparatusaccording to a sixth embodiment of the present invention;

FIG. 43 is a view of the inside of the screen printing apparatus of FIG.42, viewed from the front;

FIG. 44 is a front view of a state in which the cover of the screenprinting apparatus of FIG. 42 is open;

FIG. 45 is a right side view of the screen printing apparatus of FIG.42;

FIG. 46 is a front view showing the table section horizontal movementmechanism, the support base elevation mechanism, and the movable frameelevation mechanism of the screen printing apparatus of FIG. 42;

FIG. 47A is a right side view of FIG. 46;

FIG. 47B is an explanatory view of the board regulation mechanism ofFIG. 47A;

FIG. 48 is a flowchart showing the respective processes of the screenprinting method of the sixth embodiment;

FIG. 49 is a partial plan view showing a conventional screen printingmachine;

FIG. 50 is a front view showing another example of the conventionalscreen printing machine;

FIG. 51 is a front view showing a yet another example of theconventional screen printing apparatus;

FIG. 52 is a perspective view of the squeegee head, i.e., the printinghead section of the screen printing apparatus of the sixth embodiment;

FIG. 53 is an exploded perspective view of the printing head section ofFIG. 52;

FIG. 54 is an exploded perspective view of the mounting section of therecognition camera of the screen printing apparatus of the sixthembodiment;

FIG. 55 is an exploded perspective view of the printing head sectionhorizontal movement mechanism of the screen printing apparatus of thesixth embodiment;

FIG. 56 is a perspective view of the screen table section rotationmechanism of the screen printing apparatus of the sixth embodiment;

FIG. 57 is a perspective view of the board arrival detection sensor andso on of the screen printing apparatus of the sixth embodiment;

FIG. 58 is a perspective view of the board loader or the board unloaderof the screen printing apparatus of the sixth embodiment;

FIG. 59 is a perspective view of the board regulation mechanism and soon of the screen printing apparatus of the sixth embodiment;

FIG. 60 is a timing chart of the respective drive devices of the screenprinting apparatus of the sixth embodiment;

FIG. 61 is a block diagram showing a relation between the control unitand various drive devices of the screen printing apparatus of the sixthembodiment;

FIG. 62A, FIG. 62B, FIG. 62C, and FIG. 62D are sectional views showing acleaning device for putting a cleaning method according to a seventhembodiment of the present invention into practice executed in fiveworking processes step by step;

FIG. 63A and FIG. 63B are a plan view and an end view, respectively, ofthe backup member of the cleaning device of the seventh embodiment;

FIG. 64 is an end view showing another example of the backup member ofthe cleaning device of the seventh embodiment;

FIG. 65A and FIG. 65B are a plan view and an end view, respectively, ofthe backup member of another example of the cleaning device of theseventh embodiment;

FIG. 66 is an overall schematic view of the cleaning device of theseventh embodiment and a screen printing apparatus provided with thedevice;

FIG. 67A, FIG. 67B, FIG. 67C, and FIG. 67D are sectional views showing acleaning device for putting a cleaning method according to an eighthembodiment of the present invention into practice executed in fourworking processes step by step;

FIG. 68 is a plan view showing the backup member of the cleaning deviceof the eighth embodiment;

FIG. 69 is a side view of the backup member of the cleaning device ofthe eighth embodiment;

FIG. 70A is a transverse sectional view of the backup member of thecleaning device of the eighth embodiment; FIG. 70B is a sectional viewshowing another example of the backup member of the cleaning device ofthe eighth embodiment;

FIG. 71 is a graph showing by comparison between a cleaning effect whenthe backup member of the cleaning device of the eighth embodiment isused and that of a comparative example;

FIG. 72 is a side view showing a device for putting into practice thecleaning method of the foregoing proposed; and

FIG. 73A, FIG. 73B, FIG. 73C, FIG. 73D, and FIG. 73E are sectional viewsshowing the method of FIG. 72 executed in five working processes step bystep.

BEST MODE FOR CARRYING OUT THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

The first embodiment of the present invention will be described indetail below with reference to the drawings.

(First Embodiment)

The solder paste printing apparatus and printing method of the firstembodiment of the present invention will be described below withreference to the drawings. The printing method is executed by the solderpaste printing apparatus. Moreover, in each figure, identicalconstituent parts or those having same functions are denoted by samereference numerals, and no description is provided for them. In thisspecification, the solder paste means a solder in a paste form obtainedby mixing powdery solder with a high-viscosity flux.

FIG. 1 is a view schematically showing a squeegee and its peripherals ofa solder paste printing apparatus 10 in the first embodiment. The solderpaste printing apparatus 10 is a type such that a pair of squeegees movein both printing directions of leftward and rightward directions. Thatis, the solder paste printing apparatus 10 is provided with a squeegee12 a to be used during the rightward printing and a squeegee 12 b to beused during leftward printing.

Each of the squeegees 12 a and 12 b fills a solder paste 7 into a numberof openings 4, . . . , 4 of a printing mask 3 placed on a circuit board5 that serves as one example of the circuit-forming body during solderpaste printing and scrapes the solder paste 7 off on the printing mask3. Each of the squeegees 12 a and 12 b can independently move up anddown between a standby position 20 in which the squeegee lower end ispositioned above the printing mask 3 and an operating position 22 inwhich the squeegee lower end is in contact with the printing mask 3 bymeans of up-and-down drive devices 16 and 18 each of which isconstructed of an air cylinder or the like for the squeegee mounted on abase plate 14 of the squeegee head that constitutes the solder pasteprinting apparatus 10. The squeegees 12 a and 12 b are formed into aplate-like shape, and, for example, hard rubber such as urethane rubberis adopted as a material.

In this case, the circuit-forming body means an object on which acircuit is formed, such as a circuit board of a resin board, apaper-phenol board, a ceramic board, a glass epoxy (glass-epoxy) board,a film board, or the like, a circuit board of a single-layer board, amulti-layer board or the like; a component; a casing; or a frame.

The base plate 14 is moved in the leftward and rightward printingdirections by a drive device 26 such as a motor of which the operationis controlled by a control unit 24. FIG. 1 shows a state in which therightward printing is being performed, where one squeegee 12 apositioned on the left-hand side of FIG. 1 is moved down to theoperating position 22 for the execution of filling and scraping, and theother squeegee 12 b positioned on the right-hand side of FIG. 1 is movedup to the standby position 20.

In a state in which the squeegee 12 a or 12 b is positioned in theoperating position 22, the edge portion of each squeegee 12 a or 12 bcomes in contact with the surface 3 a of the printing mask 3 in a statein which an appropriate pressure is applied to the surface 3 a of theprinting mask 3 and performs the filling of the solder paste 7 into theopenings 4 of the printing mask 3 on the surface 3 a and the scrapingoperation on the printing mask surface 3 a.

A pressurizing member 28 is provided in the vicinity of the edge portionof each of the squeegees 12 a and 12 b.

The drive device 26 and the up-and-down drive devices 16 and 18 areconnected to the control unit 24 that executes the operation control ofthe solder paste printing apparatus 10, and the control unit 24 executesthe movement control of both the squeegees 12 a and 12 b by means of thedrive device 26 in the right-and-left directions and the up-and-downoperation control of the up-and-down drive devices 16 and 18.

FIG. 2 is a side view showing the mounting structure of a pressurizingmember provided in the vicinity of the edge portion of the squeegee 12a. FIG. 3 is a schematic view showing a relation between the squeegee 12a and the pressurizing member provided in the vicinity of the squeegee12 a. Since the other squeegee 12 b is similarly constructed, only theconstruction of one squeegee 12 a will be described.

As an example, a pressurizing member 28 is a round bar having a circularcross-section shape and fixed by a fixing member 32 such as a bracket 30and a bolt and nut so that the surface of the squeegee 12 a and thecenter axis of the pressurizing member 28 become parallel to each otherin the vicinity of the edge portion of the squeegee 12 a in thelengthwise direction, which is an example of the axial direction of thesqueegee 12 a. When the squeegee 12 a comes in contact with the printingmask 3, the pressurizing member 28 forms a narrow path 34 of a minuteinterval S between the member and the surface 3 a of the printing mask3. The interval S of this narrow path 34 is preferably about 1 mm to 3mm.

Moreover, the pressurizing member 28 forms a flow path 36 of an intervalT, which becomes the flow path of the solder paste 7 rolling during thesolder paste printing, between the member and the squeegee 12 a. Theinterval T of this flow path 36 is preferably about 1 mm to 3 mm. Asshown in FIG. 4, the rolling solder paste 7 flows on both of the upperand lower sides of the pressurizing member 28. In particular, the solderpaste 7 located under the pressurizing member 28 circulates clockwise asindicated by arrow by so as to pivot by passing through the narrow path34 between the member and the printing mask 3, thereafter passingthrough the flow path 36 located between the squeegee 12 a and thepressurizing member 28, moving over or above the pressurizing member 28in the rightward direction in FIG. 4 and passing again through thenarrow path 34.

The height of the pressurizing member 28 from the surface 3 a of theprinting mask 3, i.e., the height H2 of the upper end surface of thepressurizing member 28 is lower than the rolling height of the solderpaste 7 during printing, i.e., the height HI of the upper end surface ofthe solder paste 7 in the rolling operation, and the pressurizing member28 sinks in the rolling solder paste 7 during printing. Moreover, thepressurizing member 28 is fixed so as not to be able to rotate.

As described above, when the pressurizing member 28 is constructed of around bar, the diameter d of the round bar is preferably 2 to 10 mm, andmore particularly, is 5 to 7 mm.

By virtue of the formation of the narrow path 34 between thepressurizing member 28 and the printing mask 3, the solder paste 7 thatpasses through the narrow path 34 while rolling comes to have a higherpressure than in the conventional case in accordance with the movementof the squeegees 12 a and 12 b. As a result, the solder paste 7 isappropriately filled into the openings 4 of the printing mask 3, and theinsufficient filling attributed to a shortage of pressure of the solderpaste 7 as in the prior art technique is eliminated.

If the pressurizing member 28 warps when a high pressure is generated inthe narrow path 34, then a uniform pressure cannot be obtained in thelengthwise direction. Therefore, the pressurizing member 28 ispreferably formed of a high-rigidity material that causes no warp. Forexample, the pressurizing member 28 is formed of a metal, ceramic, orhard plastic.

FIG. 5 is a graph of the measurement results of the change in thefilling pressure of the solder paste 7 in the openings 4 while thesqueegee is operating at a high squeegee speed of 200 mm/sec. In FIG. 5,the reference letter A represents the characteristic of the squeegees 12a and 12 b provided with the pressurizing members 28, and the referenceletter B represents the characteristic of the conventional squeegeeprovided with no pressurizing member.

As shown in FIG. 17, there were measured the filling pressures with apressure sensor 51 arranged on the back surface of the printing mask 3,with the openings 4 a provided in the specified portions of the printingmask 3, and with the squeegees 12 a and 12 b moved at a travel speed of200 mm/sec.

Time t on the horizontal axis is the time during which the squeegees 12a and 12 b pass over the pressure sensor 51, and the filling pressure Pon the vertical axis is the pressure detected by the pressure sensor 51via the solder paste 7 when the squeegees 12 a and 12 b pass over thepressure sensor 51.

As is apparent from this graph, the squeegees 12 a and 12 b providedwith the pressurizing members 28 produce a required pressure (forexample, Pf shown in the figure) or more needed for the filling during alonger time even if the squeegee speed is increased, whereas theconventional squeegee produces the required pressure Pf needed for thefilling during only a shorter time when the squeegee speed is increased.

Therefore, it can be understood that the solder paste 7 is sufficientlyfilled into the openings 5 of the printing mask 3 even when the squeegeespeeds of the squeegees 12 a and 12 b provided with the pressurizingmembers 28 are increased.

As described above, in the case of the pressurizing member 28constructed of a round bar, the cross-section shape of the introducingportion of the narrow path 34 is formed into a roughly wedge-like shapeby the curved surface of the round bar of the pressurizing member 28,and therefore, the pressure can be increased with the solder paste 7drawn in.

Moreover, the narrow path 34 may have a wedge-like cross-section shapeas shown in FIG. 6 and FIG. 7 for the same purpose. FIG. 6 shows aconstruction in which a pressurizing member 28A is a rod that has asemicircular cross-section shape and an inclined flat surface 28 a onthe lower side, and this pressurizing member 28A forms the narrow path34 of the wedge-like cross-section shape. FIG. 7 shows a construction inwhich a pressurizing member 28B is obtained by processing a rod that hassemicircular cross-section shape to have a wedge-like cross-sectionshape with its outer peripheral surface partially left so that thepressurizing member has an inclined flat surface on the upper side andthe inclined flat surface 28 a on the lower side, and this pressurizingmember 28B forms the narrow path 34 of a wedge-like cross-section shape.

It is to be noted that the cross-section shape of the narrow path 34located between the pressurizing member 28, 28A, or 28B and the printingmask 3 is not especially limited, and it is acceptable only to form anarrow gap between the pressurizing member and the printing mask 3.

The narrow path 34 is only required to generate a gap of about 0.5 mm to10 mm between the pressurizing member 28, 28A, or 28B and the printingmask 3 as described above, and it is particularly preferable to generatea gap of about 1 mm to 3 mm.

As shown in FIG. 6 and FIG. 7, if the surface 28 a that belongs to eachof the pressurizing members 2BA and 28B and faces the printing mask 3 isan inclined surface for the formation of the narrow path 34 of thewedge-like cross-section shape, then an angle of inclination θ withrespect to the printing mask 3 is preferably about 30 degrees. Even ifthe shape of the pressurizing member 28 is changed to that of thepressurizing member 28A or 28B as described above, the filling pressureof the solder paste 7 into the openings 4 of the printing mask 3 roughlyobtains the characteristic of A shown in FIG. 5, and the requiredpressure needed for the filling is generated for a longer time than inthe conventional case.

Moreover, it is preferred that a pressurizing member 28C has a built-inheat-generating element 38 as shown in FIG. 8 and appropriately heatsthe solder paste 7 up to a temperature of about 20 to 30° C. Thepressurizing member 28C having the built-in heat-generating element 38appropriately heats the solder paste 7 and maintains the temperature ofthe solder paste 7 constant, by which the viscosity of the solder paste7 is maintained constant, allowing a stable filling characteristic to beobtained.

The solder paste printing operation by the solder paste printingapparatus 10 constructed as above will be described below with referenceto FIG. 9.

In step (indicated by “S” in FIG. 9) 1, the following operation isperformed. First of all, a prescribed amount of solder paste 7 issupplied to the surface 3 a of the printing mask 3. The printed board 5is moved up to a printing position and held by a printed board elevationdevice or the like (not shown), and the printed board 5 is positionedand layered with the printing mask 3 so that the openings 4 of theprinting mask 3 is positioned on the lands 6 of the printed board 5.Then, in the case of rightward printing, the rightward printing squeegee12 a is moved down by the up-and-down drive device 16 under the controlof the control unit 24. At this time, the edge portion 20 of thesqueegee 12 a is brought in contact with the surface 3 a of the printingmask 3 with a proper application pressure. The leftward printingsqueegee 12 b is made to stay in the standby position by the up-and-downdrive device 18.

In step 2, the base plate 14 is moved rightward in FIG. 1 by the drivedevice 26 under the control of the control unit 24 in a state in whichthe rightward printing squeegee 12 a is brought in contact with thesurface 3 a of the printing mask 3 with a proper application pressure,linearly moving the squeegee 12 a in the rightward printing direction.By this operation, the filling operation of the solder paste 7 into theopenings 4 of the printing mask 3 by the squeegee 12 a and the scrapingoperation on the surface 3 a of the printing mask 3 are started in step3. At this time, the solder paste 7 that is rolling on the surface 3 aof the printing mask 3 flows clockwise around the pressurizing member 28as shown in FIG. 4. In particular, the solder paste 7 located on thelower side of the pressurizing member 28 circulates so as to passthrough the narrow path 34 located between the member and the printingmask 3 in the leftward direction opposite to the printing direction,thereafter pass through the flow path 36 located between the squeegee 12a and the pressurizing member 28 upwardly aslant to the right, move tothe upper right-hand side of the pressurizing member 28 in FIG. 4, moveto the lower right-hand side and pass again through the narrow path 34.By the passing of the solder paste 7 through this narrow path 34, thefilling pressure is made higher than in the conventional case, and thesolder paste 7 is sufficiently filled into the openings 4 even if thesqueegee speed is increased.

In step 4, when the squeegee 12 a arrives at a movement end position,the movement of the squeegee 12 a is stopped by the drive device 26under the control of the control unit 24.

Subsequently, in step 5, the printed board 5 is moved down by theprinted board elevation device or the like (not shown) to separate theprinted board 5 from the printing mask 3, completing the printing of thesolder paste 7.

Next, during the leftward printing, similar to the aforementionedrightward printing, the printed board 5 is moved up to the printingposition and held by the printed board elevation device or the like (notshown), and the printed board 5 is positioned and layered with theprinting mask 3 so that the openings 4 of the printing mask 3 ispositioned on the lands 6 of the printed board 5. Thereafter, theleftward printing squeegee 12 b is moved down by the up-and-down drivedevice 18 under the control of the control unit 24. Also, at this time,the edge portion of the squeegee 12 b is brought in contact with thesurface 3 a of the printing mask 3 with a proper application pressure.At this time, the rightward printing squeegee 12 a is made to stay inthe standby position by the up-and-down drive device 16. The subsequentoperation is performed similarly to the aforementioned rightwardprinting. By alternately repeating the printing operations as describedabove, the solder paste 7 is continuously printed on the lands 6 of theprinted board 5 via the printing mask 3.

It is to be noted that the solder paste printing apparatus 10 of thefirst embodiment is the type of the movement in both the leftward andrightward printing directions, and therefore, both the squeegees 12 aand 12 b are provided. However, the solder paste printing apparatus maybe the type of the movement only in either one direction, and in such acase, the squeegee 12 a or the squeegee 12 b corresponding to thedirection of movement is provided.

(Second Embodiment)

Moreover, the first embodiment has the construction in which thesqueegees 12 a and 12 b are vertically moved. However, as in FIG. 10showing the solder paste printing apparatus of the second embodiment ofthe present invention, both the squeegees may consistently brought incontact with the surface 3 a of the printing mask 3 without the vertical(up-and-down) movement during printing. The printing apparatus shown inFIG. 10 executes the filling and scraping operations of the solder paste7 in the state in which a pair of squeegees 12 a, 12 b are consistentlybrought in contact with the printing mask 3 during printing, releasesthe application pressure that has been applied when the movement of thesqueegees 12 a and 12 b is ended, and then separates the printed board 5from the printing mask 3. By repeating this operation, the printing iscontinuously performed. By this operation, the solder paste 7 isconsistently held between both the squeegees 12 a and 12 b, and theup-and-down movement of the squeegees 12 a and 12 b can be eliminated,allowing the printing time to be further reduced. When the printingends, both the squeegees 12 a and 12 b are moved up by the drive devices16 and 18 and held in the standby position 20. Since the printingapparatus shown in FIG. 10 has the same construction as that of theprinting apparatus shown in FIG. 1 although the operation control isvaried, no description is provided for the construction.

It is to be noted that the reference numeral 50 denotes a side plateprovided so as to stride over either one or both of the squeegees 12 aand 12 b and is able to prevent the solder paste 7 from moving into aposition displaced from the squeegees 12 a and 12 b in the axialdirection of the squeegees 12 a and 12 b.

Furthermore, although the squeegees 12 a and 12 b are driven by theup-and-down drive devices 16 and 18 independently from each other, it isacceptable to mount both the squeegees on one up-and-down drive device.

The working examples of the present invention will be described next. Itis to be noted that the squeegee speed in each of the following workingexamples is 200 m/sec increased from the conventional squeegee speed (40mm/sec).

WORKING EXAMPLE 1

Printing was performed by setting a squeegee angle α to 60 degrees inthe conventional squeegee provided with no pressurizing member and thesqueegee of the working example 1 of the present invention provided withthe pressurizing member constructed of a round bar in order to observe achange in the filling pressure depending on the presence or absence ofthe pressurizing member and a change in the squeegee angle. A squeegeemade of urethane rubber was adopted.

Sample a (working example 1): provided with the pressurizing member.

Sample b (comparative example): provided with no pressurizing member.

It is to be noted that a round bar having a diameter of 5 mm was used asa pressurizing member for the Sample a, the gap between the pressurizingmember and the printing mask was set to 3 mm, and the gap between thepressurizing member and the squeegee was set to 1 mm.

FIG. 11 shows the results.

As apparent from the graph shown in FIG. 11, when the pressurizingmember existed as in the case of the Sample a, the high-pressure statewas able to be maintained for a long time. Therefore, it can beunderstood that satisfactory printing can be performed even if thesqueegee speed is increased. In contrast to this, when no pressurizingmember existed as in the case of the Sample b, a sufficient pressure wasnot able to be obtained. This indicates that the pressurizing member isextremely effective.

WORKING EXAMPLE 2

In the working example 2, the printing conditions depending on a changein the cross-section shape of the pressurizing member was observed.Other printing conditions are roughly similar to those of the workingexample 1.

Sample e: a circular cross-section having a diameter d of 5 mm.

Sample f: a semicircular cross-section having a diameter d of 5 mm, andthe angle θ with respect to the printing mask is set to 30 degrees (FIG.6).

Sample g: a semicircular cross-section having a diameter d of 8 mm, andthe angle e with respect to the printing mask is set to 30 degrees (FIG.6).

Sample h: a semicircle having a diameter d of 8 mm is processed into awedge-shaped cross-section with an angle β set to 30 degrees leaving thediametrical surface, and the angle θ with respect to the printing maskis set to 30 degrees (FIG. 7).

Sample i: a circular cross-section having a diameter d of 6 mm.

Sample j: a circular cross-section having a diameter d of 7 mm.

Sample k: provided with no pressurizing member (comparative example).

FIG. 12 shows the results.

As apparent from the results shown in FIG. 12, high-pressure states wereable to be maintained for a longer time than in the conventional case inthe presence of the pressurizing members of the Samples e to j.Therefore, it can be understood that satisfactory printing can beperformed even if the squeegee speed is increased and the pressurizingmember is extremely effective.

Moreover, in the cases of the Samples e, i, and j in which the roundbars having a diameter d of 5 mm, 6 mm, and 7 mm are used as thepressurizing members, there is no need for the complicated mechanicalprocessing of the material for manufacturing the pressurizing members,and the pressurizing members can be provided with a simple construction.Therefore, the pressurizing members can be provided without increasingthe manufacturing cost, which are more effective.

Moreover, according to FIG. 12, a higher pressure state can bemaintained for a longer time than in the conventional case whichevercross-section shape the pressurizing members have. Therefore, thecross-section shape of the pressurizing member is not limited to thecross-section shape shown in the working examples and is merely requiredto be such a shape that the narrow path is formed between thepressurizing member and the printing mask.

According to the first embodiment and the second embodiment, byproviding the pressurizing members 28, 28A, 28B, 28C, and 28D that formthe narrow paths 34 between the members and the printing masks 3 andform the flow paths 36 between the members and the squeegees 12 a and 12b in the vicinity of the edge portions of the squeegees 12 a and 12 b,the solder paste 7 that is rolling during the movement of the squeegeefor solder paste printing passes through the narrow path 34, as aconsequence of which the higher pressure state than in the conventionalcase can be provided by the narrow path 34. That is, the pressure of thesolder paste 7 that is flowing between the pressurizing members 28, 28A,28B, 28C, and 28D and the printing masks 3 is increased further than inthe conventional case, and a larger amount of solder paste 7 flowsdownward by the increased pressure so as to be filled into the openings4 of the printing mask 3. The pressurizing members 28, 28A, 28B, 28C,and 28D form the narrow path 34 between the members and the surface 3 aof the printing mask 3, and therefore, the solder paste 7 that isflowing between the pressurizing members 28, 28A, 28B, 28C, and 28D andthe surfaces 3 a of the printing masks 3 maintains the high pressure fora long time. Therefore, even if the squeegee speed is increased, thesolder paste 7 is sufficiently filled into the openings 4 when thepressurizing members 28, 28A, 28B, 28C, and 28D face the openings 4 ofthe printing masks 3, and a shortage of filling is eliminated.

Moreover, when the pressurizing member 28 is constructed of a round bar,there is no need for the complicated mechanical processing of thematerial in manufacturing the pressurizing member 28, and thepressurizing member 28 can be provided with a simple construction.Therefore, the manufacturing cost is not increased.

Moreover, when the pressurizing member 28C has the built-inheat-generating element 38, the temperature of the solder paste 7 can bemaintained constant. Consequently, the viscosity of the solder paste 7is maintained constant, and constant printing characteristics areobtained.

Moreover, particularly in the second embodiment, a pair of squeegees 12a and 12 b is provided, and both the squeegees 12 a and 12 b areconsistently brought in contact with the printing mask 3 at least duringprinting. Therefore, the take-out of the solder paste 7 by the risingsqueegees 12 a and 12 b is prevented, and the set amount of solder paste7 can be consistently held on the printing mask 3. Moreover, neither thesqueegee 12 a nor 12 b vertically moves during printing. Therefore, theprinting time can be reduced, and the productivity can be improved.

Moreover, as shown in FIG. 26A, if the printing is repetitivelyperformed with the conventional construction, the solder paste 7 isprotruded from both sides of the squeegee 12 a. The solder paste 7Aprotruded therefrom does not naturally return, and the operator collectsand puts back the paste at regular intervals of time or dispose of it.In contrast to this, by applying a pressure to the solder paste 7 withthe pressurizing members 28, 28A, 28B, 28C, and 28D arranged, the solderpaste 7 rolls around the pressurizing members 28, 28A, 28B, 28C, and 28Dand comes to surround the pressurizing members 28, 28A, 28B, 28C and28D. Therefore, even if the printing is repeated, as shown in FIG. 26B,a large amount of solder paste is not protruded dissimilar to theconventional case. Therefore, the work of the operator can be reducedand the productivity can be improved.

Furthermore, the pressurizing members 28, 28A, 28B, 28C, and 28D aremerely supported with interposition of a specified gap to the squeegees12 a and 12 b, and no tightly closing portion exists. Therefore, whencleaning the squeegee and the like, the cleaning can be simplyperformed.

Moreover, since the narrow path 34 has a roughly wedge-shapedcross-section shape, the solder paste 7 is efficiently introduced by theinclined surfaces 28 a of the pressurizing members 28, 28A, 28B, 28C,and 28D, and the pressure of the solder paste 7 that is flowing betweenthe pressurizing members 28, 28A, 28B, 28C, and 28D and the surfaces 3 aof the printing masks 3 can be efficiently increased.

Moreover, the height H2 of the pressurizing members 2B, 28A, 28B, 28C,and 28D from the surfaces 3 a of the printing masks 3 is lower than therolling height H1 of the solder paste 7 during printing, and thepressurizing members 28, 28A, 28B, 28C, and 28D sink in the rollingsolder paste 7 during the printing. Therefore, the pressurizing members28, 28A, 28B, 28C, and 28D exert no bad influence on the rolling of thesolder paste 7, and the pressure of the solder paste 7 that is flowingbetween the members and the surfaces 3 a of the printing masks 3 can beincreased.

Moreover, the pressurizing members 28, 28A, 28B, 28C, and 28D, which arefixed so as to be unable to rotate, can be mounted with a simpleconstruction.

It is to be noted that the present invention is not limited to theaforementioned embodiments and is able to be put into practice in avariety of forms. For example, with regard to the cross-section shape ofthe pressurizing member 28D in the direction perpendicular to the axialdirection, by varying the diametrical dimension so as to construct themember of a large-diameter portion 28 t in the axial direction of thepressurizing member 28D and a small-diameter portion 28 s of a diametersmaller than that of the large-diameter portion 28 t as shown in FIG.26C depending on the number and the size of the openings 4 of theprinting mask 3, the pressure applied to the solder paste 7 by thepressurizing member 28D can be varied. For example, in the region wherea lot of openings 4 of the printing mask 3 exist or are arranged at highdensity, it is required to increase the filling pressure with thelarge-diameter portion 28 t arranged oppositely, and it is preferable toarrange the small-diameter portion 28 s oppositely to provide a normalpressure in the other regions. More concretely, for example, in thehigh-filling region in which the openings 4, . . . , 4 of a largeprinting mask 3 of a square having a side of not smaller than 2 mm orthe like are concentrated or in the high-filling region in which minuteopenings 4, . . . , 4 corresponding to the narrow pitch pattern of the0.3-mm pitch QFP (Quad Flat Package) pattern of an area of about 0.15mm×1.4 mm, a 0.5-mm pitch CSP (Chip Size Package) pattern of a diameterof about 0.25 mm, or the like, the cross-section shapes of thepressurizing members 28, 28A, 28B, 28C, and 28D perpendicular to theaxial direction are increased to enable the application of a higherpressure to the solder paste 7 by the pressurizing members 28, 28A, 28B,28C, and 28D. On the other hand, other than the aforementioned case, inthe low-filling region where openings 4 of a normal size are sparselyarranged, the cross-section shape of the pressurizing members 28, 28A,28B, 28C, and 28D perpendicular to the axial direction is reduced toenable the application of a pressure lower than in the high-densityregion to the solder paste 7 by the pressurizing members 28, 28A, 28B,28C, and 28D.

(Third Embodiment)

In the solder paste printing apparatus of the third embodiment of thepresent invention, as shown in FIG. 20 through FIG. 23, the pressurizingmember 28 of a round bar is rotated in the direction opposite to therolling direction of the solder paste 7.

The pressurizing member 28 of a round bar is rotatably supported by apair of brackets 30 and 30, one end of the pressurizing member 28 ismade to project from one bracket 30, and a pulley 53 is fixed to theprojecting end. A motor 49 is arranged in the vicinity of thepressurizing member 28 of the one bracket 30, and a pulley 52 fixed to arotary shaft of motor 49 and the pulley 53 located at the projecting endportion of the pressurizing member 28 are connected to each other bymeans of a belt 54. With this arrangement, if the rotary shaft of themotor 49 is rotated counterclockwise in FIG. 20, then the pressurizingmember 28 is to be rotated counterclockwise (in a direction of the arrowY in FIG. 22) via the pulley 52, the belt 54, and the pulley 53, bywhich the pressurizing member 28 can be rotated in the directionopposite to the flow (rotational flow in the direction of the arrow X inFIG. 22) of the rolling solder paste 7 during printing in the rightwarddirection in FIG. 20. If the motor 49 is connected to the control unit24, then the motor 49 can be controlled to be rotatively driven by thecontrol unit 24 during printing or immediately before the printing.

It is to be noted that the rotary mechanism of the pressurizing member28 may connect the motor 49 directly to the pressurizing member 28 ortake similar measures, and the present invention is not limited to theaforementioned construction.

According to the aforementioned construction, as shown in FIG. 22, byrotating the pressurizing member 28 in the direction of the arrow Yopposite to the direction of the arrow X of the direction in which therolling solder paste 7 flows during printing, it is more difficult forthe solder paste 7 to pass through the narrow path 34 and the flow path36 than when the pressurizing member 28 is fixed so as to be unable torotate. In general, the pressure of the fluid such as the solder paste 7is increased when the fluid becomes uneasy to flow, and therefore, asshown in FIG. 23C, the filling pressure is further increased than in thecase of FIG. 23A (corresponding to FIG. 5A). Therefore, a shortage offilling attributed to a shortage of filling pressure of the solder pasteis eliminated dissimilar to the conventional case. That is, FIG. 23Cshows the case of a squeegee provided with the pressurizing member ofthe solder paste printing apparatus of the third the embodiment. Thereference letter A indicates the case of the squeegee provided with thepressurizing member of the solder paste printing apparatus of the firstembodiment. The reference letter B indicates the case of a squeegeeprovided with no pressurizing member.

(Fourth Embodiment)

In the solder paste printing apparatus of the fourth embodiment of thepresent invention, as shown in FIG. 24 and FIG. 25, the pressurizingmember 28 may be mounted on the squeegees 12 a and 12 b while being ableto be opened and closed by an openable mechanism, facilitating thecleaning of the lodging solder paste and the like.

Although the pressurizing members 28A, 28B, and 28C can also be appliedsimilarly to the pressurizing member 28, the pressurizing member 28 willbe described as a representative for the simplicity of explanation.

In the fourth embodiment, both ends of the pressurizing member 28 aresupported not by the bracket 30 but by a retention member 45. Theretention member 45 is mounted on a holder 33 for holding the squeegee12 a via a fitting member 48 while being able to pivot at an angle of atleast 90 degrees around a pin 47 for opening and closing, i.e., betweena pressurizing position P1 where the pressurizing member 28 applies apressure to the solder paste 7 and a retreated position P2 where theapplying of pressure is released and able to be positioned and held ineach position. A fixing bolt 46 is mounted on the retention member 45while being rotatably held and unable to be dismounted. By screwing thefixing bolt 46 into a threaded hole 33 a of the holder 33, the retentionmember 45 contacts the holder 33, enabling the positioning of thepressurizing member 28 supported by the retention member 45 in thepressurizing position P1.

Therefore, during the solder paste printing, as shown in FIG. 24, byfixing the retention member 45 to the holder 33 by means of the fixingbolt 46 and positioning and holding the pressurizing member 28 in thepressurizing position P1, a specified pressure is applied to the solderpaste 7. When the cleaning of the squeegee 12 a is needed at the time ofthe end of the solder paste printing, board type change, or the like, asshown in FIG. 25, by loosening the fixing bolt 46, pulling out thefixing bolt 46 from the threaded hole 33 a of the holder 33, thereafterrotating the retention member 45 counterclockwise at an angle of 90degrees around the pin 47 for opening and closing and positioning, andholding the member in the retreated position P2, the retention member 45can be kept in the open state.

With the above-mentioned construction, the pressurizing member 28 isseparated from the squeegee 12 a during, for example, cleaning.Therefore, the squeegee does not become an impediment, and the cleaningwork of the solder paste 7 that has stuck to the squeegee 12 a can beeasily performed, improving the maintenance.

FIG. 27 shows a graph and an explanatory view of a change depending onthe arrangement of the pressurizing member 28 of a round bar. It isassumed that an interval S of the narrow path 34 is 1 mm, 2 mm, 3 mm,and 5 mm when an interval T of the flow path 36 is 1 mm, 2 mm, and 3 mmwhen the angle of inclination θ of the squeegee is fixed to 60 degrees.At this time, the pressure given to the solder paste, i.e., theapplication pressure P is measured, and a solder rolling property, asolder scraping state on the printing mask and a printing state areevaluated. The solder rolling property, the solder scraping state on theprinting mask and the printing state are visually evaluated, when themark ∘ indicates the satisfactory state and the mark Δ represents theunsatisfactory state. According to this FIG. 27, the solder rollingproperty, the solder scraping state on the printing mask, and theprinting state are all satisfactory when the interval S of the narrowpath 34 is 1 mm, 2 mm, and 3 mm when the interval T of the flow path 36is 1 mm and 2 mm. However, when the interval S of the narrow path 34 is5 mm, the solder rolling property and the printing state become alldefective.

According to this FIG. 27, it can be understood that the interval T ofthe flow path 36 is preferably about 1 mm to 3 mm and that the intervalS of the narrow path 34 is preferably about 1 mm to 3 mm.

FIG. 28A, FIG. 28B, and FIG. 29 show a relation between the printingspeed and the filling pressure profile. FIG. 28A is an explanatory viewshowing a relation between the board and the printing direction. FIG.28B shows a filling pressure profile of a relation between the fillingpressure and time when the printing speed is changed in five steps from40 mm/sec to 400 mm/sec when the squeegee is provided with nopressurizing member. FIG. 29 shows a filling pressure profile of arelation between the filling pressure and time when the printing speedis changed in five steps from 40 mm/sec to 400 mm/sec when the squeegeeis provided with the pressurizing member 28 of a round bar.

FIG. 30 shows a relation between the type (viscosity) of the solderpaste and the printing conditions when the squeegee is provided with nopressurizing member. FIG. 31 shows a relation between the type(viscosity) of the solder paste and the printing conditions when thesqueegee is provided with the pressurizing member 28 of a round bar. InFIG. 30 and FIG. 31, the state of the scraping state, the solder rollingproperty on the printing mask, and the filling (printing) state arevisually evaluated. The mark ∘ represents the satisfactory state, themark Δ represents the unsatisfactory state, and the mark x representsthe defective state. The printing pressure is-set to 0.08 to 0.20 N/mm.

Comparing FIG. 30 with FIG. 31, it can be understood that the scrapingstate, the solder rolling property on the printing mask, and the filling(printing) state become satisfactory even when the printing speed isfast in the presence of the pressurizing member of a round bar of FIG.31 in all the cases of the solders of the materials A through I.

It is to be noted that, by appropriately combining arbitrary embodimentsout of the aforementioned various embodiments, the effects owned by theembodiments can be produced.

According to the present invention, the pressurizing member, which formsthe narrow path between the member and the printing mask and the flowpath between the member and the squeegee during printing, is provided inthe vicinity of the edge portion of the squeegee. With this arrangement,the rolling solder paste during the squeegee movement passes through thenarrow path, by which a higher pressure than in the conventional casecan be applied. Therefore, even if the squeegee speed is increased, thesolder paste is sufficiently filled into the openings when thepressurizing member faces the openings of the printing mask, and ashortage of filling is eliminated.

Moreover, the pressurizing member is mounted so as to be movable betweenthe pressurizing position where a pressure is applied to the solderpaste and the retreated position where the applying of pressure isreleased, with respect to the squeegee. With this arrangement, when thecleaning of the squeegee is needed at the time of the end of the solderpaste printing, board type change, or the like, the squeegee can bepositioned in the retreated position. Therefore, the pressurizing membercan be separated from the squeegee during cleaning or the like and doesnot become an impediment, by which the cleaning work of the solder pastethat has stuck to the squeegee can easily be performed, improving themaintenance.

Moreover, when the introducing portion of the cross-section shape of thenarrow path is formed into a roughly wedge-like cross-section shape withthe curved surface or the like of the round bar of the pressurizingmember, the pressure can be increased while drawing the solder pasteinto the narrow path.

Moreover, when the pressurizing member has the built-in heat-generatingelement to appropriately heat the solder paste, the viscosity of thesolder paste is maintained constant by maintaining the solder pastetemperature constant, and stable filling characteristics can beobtained.

Moreover, when the pressurizing member is constructed of a round bar,there is no need for subjecting the material to the complicatedmechanical processing in manufacturing the pressurizing member, and thepressurizing member can be provided with a simple construction.Therefore, the manufacturing cost is not increased.

Moreover, when a pair of squeegees is provided and both the squeegeesare consistently brought in contact with the printing mask at leastduring printing, the take-out of the solder paste by the risingsqueegees is prevented, and the set amount of solder paste can beconsistently kept on the printing mask. Moreover, the squeegee does notvertically move during printing. Therefore, the printing time can bereduced, and the productivity can be improved.

Moreover, if the printing is repetitively performed with theconventional construction, the solder paste is protruded from both sidesof the squeegee. The solder paste protruded therefrom does not naturallyreturn, and the operator collects and puts back the paste at regularintervals of time or dispose of it. In contrast to this, by applying apressure to the solder paste with the pressurizing member arranged, thesolder paste rolls around the pressurizing member and comes to surroundthe pressurizing member. Therefore, even if the printing is repeated, alarge amount of solder paste is not protruded dissimilar to theconventional case. Therefore, the work of the operator can be reducedand the productivity can be improved.

Furthermore, the pressurizing member is merely supported withinterposition of a specified gap to the squeegee, and no tightly closedportion exists. Therefore, when cleaning the squeegee and the like, thecleaning can be simply performed.

Moreover, when the narrow path has a roughly wedge-shaped cross-sectionshape, the solder paste is efficiently introduced by the inclinedsurface of the pressurizing member, and the pressure of the solder pastethat is flowing between the pressurizing member and the surface of theprinting mask can be efficiently increased.

Moreover, when the height of the pressurizing member from the surface ofthe printing mask is lower than the rolling height of the solder pasteduring printing, and the pressurizing member sinks in the rolling solderpaste during the printing, the pressurizing member exerts no badinfluence on the rolling of the solder paste, and the pressure of thesolder paste that is flowing between the member and the surface of theprinting mask can be increased.

Moreover, when the pressurizing member is fixed so as to be unable torotate, the member can be mounted with a simple construction.

Moreover, by varying the cross-section shape perpendicular to the axialdirection of the pressurizing member in the axial direction of thepressurizing member depending on the number and the size of the openingsof the printing mask, the pressure applied to the solder paste by thepressurizing member can be varied.

Moreover, when the pressurizing member is rotated in the directionopposite to the direction of the flow of the rolling solder paste duringprinting, it is more difficult for the solder paste to pass through thenarrow path and the flow path than when the pressurizing member isarranged fixed so as to be unable to rotate. In general, the pressure ofthe fluid such as the solder paste is increased when the fluid becomesuneasy to flow, and therefore, the filling pressure is furtherincreased. Therefore, a shortage of filling attributed to a shortage offilling pressure of the solder paste is eliminated dissimilar to theconventional case.

(Fifth Embodiment)

The fifth embodiment of the present invention will be described indetail below with reference to FIG. 32 through FIG. 41. In each figure,the same components or the constituent elements that produce the samefunctions are denoted by the same reference numerals, and no descriptionis provided for them.

In the conventional solder paste printing apparatus, it is required tomanually appropriately set various printing conditions of squeegeetravel speed, squeegee contact pressure, and so on during printing onthe basis of the rule of thumb in order to maintain a satisfactoryprinting state while increasing the printing speed, and this settingwork has required skill.

Accordingly, the solder paste printing apparatus and printing method ofthe fifth embodiment of the present invention solves the aforementionedconventional issues and enables a satisfactory printing state to bestably maintained while increasing the printing speed by simply settingoptimum printing conditions.

FIG. 32 is a view of a solder paste printing machine 1 equipped with thesolder paste printing apparatus 210 of the fifth embodiment, with a partthereof removed. In FIG. 32, the solder paste printing machine 1 isconstructed of a printed board conveying section 1A for loading andunloading a printed board (circuit board) 5 that serves as one exampleof the circuit-forming body that is the object on which the solder pasteis to be printed into and from the printing machine 1, a table section1B which moves to a portion under the printing mask 3 and on which theprinted board 5 is placed, and a printing section 1C for printing asolder paste on the upper surface of the printed board 5 that ispositioned under the lower surface of the printing mask 3 and layeredwith the mask and the printing mask 3 by means of a squeegee. If thesolder paste printing apparatus 10 of the first through fourthembodiments is arranged in place of the solder paste printing apparatus210 of FIG. 32, a solder paste printing machine equipped with the solderpaste printing apparatus 10 of the first through fourth embodiments isprovided.

According to the solder paste printing machine 1 equipped with thesolder paste printing apparatus 210 of this fifth embodiment, theprinted board conveying section 1A receives the printed board 5 loadedfrom a printed board stocker and a printed board conveyance line andsupplies the printed board 5 to the table section 1B arranged inside theprinting machine. Then, the table section 1B positions and fixes thesupplied printed board 5 and moves the board into a specified positionunder the lower surface of the printing mask 3 of the printing section1C. When the printing in the printing section 1C ends, the table section1B conveys the printed board 5 from the printing section 1C to theprinted board conveying section 1A. Thereafter, the printed boardconveying section 1A takes out the printed board 5 from the tablesection 1B and discharges the printed board 5 to an unloading port (notshown).

FIG. 33 shows the detailed construction of the table section 1B. Thetable section 1B is provided with a board placement base 243 that fixesthe printed board 5 by a pair of holding members 241 and is able to bemoved and rotated by motor control in the directions of X, Y, Z, and θshown in FIG. 33, a board recognizing camera 245 for recognizing thepositional alignment marks (refer to 1005A and 1005B) on the printedboard 5 and a printing mask recognizing camera 247 for recognizing thealignment marks (refer to 1003A and 1003B) on the printing mask 3.

The board recognizing camera 245 images the positional alignment marks1005A and 1005B preparatorily provided on the printed board 5 that isthe object to be printed supplied to the table section 1B by the printedboard conveying section 1A. By recognizing the mark positions throughthe image processing of this pick-up image, the printed board 5 can bepositioned with high accuracy in the specified position for theprinting.

The printing mask recognizing camera 247 images the positional alignmentmarks 1003A and 1003B preparatorily provided on the printing mask 3 forthe printing of the printed board 5. By recognizing the mark positionsthrough the image processing of this pick-up image, the printed board 5can be positioned with high accuracy in the proper positioncorresponding to the pattern of the printing mask 3.

A loader and an unloader, which are generally widely used, can be usedfor the printed board conveying section 1A. Moreover, as shown in FIG.34, a four-axis stage 240, which has a total of four axes of X, Y, Z,and 8 and are generally widely used, can be used for the table section1B. That is, in FIG. 34, a threaded shaft 240Z1 is rotated forwardly andreversely by forwardly and reversely rotating, for example, a motor 240Zin the Z-direction, and then, an X-stage 240 a to which a nut membermeshed with the threaded shaft 240Z1 is fixed advances and retreats inthe Z-direction. In an X-direction perpendicular to the Z-direction, amotor 240X is rotated forwardly and reversely to rotate a threaded shaft240X1 forwardly and reversely, and then, a Y-stage 240 b to which a nutmember meshed with the threaded shaft 240X1 is fixed advances andretreats in the X-direction. Moreover, in a Y-direction perpendicular tothe X-direction, a motor 240Y is rotated forwardly and reversely torotate a threaded shaft motor 240Y1 forwardly and reversely, and then, aθ-stage 240 c to which a nut member meshed with the threaded shaft motor240Y1 advances and retreats in the Y-direction. Moreover, in theθ-direction around the center axis of the board placement base 243, amotor 240θ is rotated forwardly and reversely to rotate a threaded shaft240θ1 forwardly and reversely, and the board placement base 243 to whicha nut member meshed with the threaded shaft is fixed rotates forwardlyand reversely clockwise or counterclockwise in the θ-direction.

FIG. 35 shows a perspective view of the printing section 1C with a partthereof shown sectionally. Although the detailed construction of theprinting section 1C will be described later, the section roughly has aconstruction such that the solder paste 7 is printed on the printedboard 5 by moving a pair of squeegees 12 a and 12 b horizontally on theprinting mask 3 in both the rightward and leftward printing directionsin a state in which the printed board 5 fixed on the board placementbase 243 by the holding members 241 is arranged under the printing mask3. In this case, the squeegee 12 a is used during the rightwardprinting, and the squeegee 12 b is used during the leftward printing.However, it is also acceptable to perform the rightward printing or theleftward printing or the rightward printing and leftward printing byconcurrently bringing both the squeegees 12 a and 12 b in contact withthe printing mask 3 as in the second embodiment.

FIG. 36 is a view showing the schematic construction of the periphery ofthe squeegee of a solder paste printing apparatus 210 that is oneconcrete example of the printing section 1C. The solder paste printingapparatus 210 of the fifth embodiment fills the solder paste 7 into anumber of openings 4 of the printing mask 3 during printing. Moreover,the squeegees 12 a and 12 b that perform the scraping operation of thesolder paste 7 on the printing mask 3 are each constructed so as to beable to move up and down between the standby position 20 where the lowerend of the squeegee is positioned above the printing mask 3 and theoperating position 22 where the lower end of the squeegee is put incontact with the printing mask 3 as in the first embodiment by thesqueegee up-and-down drive devices 16 and 18 each of which isconstructed of an air cylinder or the like mounted on the base plate 14of the squeegee head that constitutes the solder paste printingapparatus 210. The squeegees 12 a and 12 b are formed into a plate-likeshape, and, for example, hard rubber such as urethane rubber is adoptedas the material.

The base plate 14 is moved in the leftward and rightward printingdirections by the printing drive device 26 such as a motor of which theoperation is controlled by the control unit (control means) 24. FIG. 36shows the state in which the rightward printing is being performed,where one squeegee 12 a located on the left-hand side in FIG. 36 movesdown to the operating position 22 where the filling and scrapingoperations are performed, and the other squeegee 12 b located on theright-hand side in FIG. 34 is moved up to the standby position 20.

In the state in which the squeegee 12 a or 12 b is located in theoperating position 22, the edge portion of each squeegee comes incontact with the surface 3 a of the printing mask 3 in a state in whichthe proper application pressure is applied to the surface 3 a of theprinting mask 3 and performs the filling of the solder paste 7 into theopenings 4 of the printing mask 3 and the scraping operation on theprinting mask surface 3 a.

A pressurizing member 28 described in detail later is provided in thevicinity of the edge portions of the squeegees 12 a and 12 b.

Moreover, the printing drive device 26 and the squeegee up-and-downdrive devices 16 and 18 of the base plate 14 are each connected to thecontrol unit 24 that executes overall operation control of the solderpaste printing apparatus 210, and the control unit 24 controls the rightand left movement control of both the squeegees 12 a and 12 b by meansof the drive device 26 and the up-and-down movement control of theup-and-down drive devices 16 and 18.

FIG. 37 is a side view showing the mounting construction of thepressurizing member 28 provided in the vicinity of the edge portion ofthe squeegee 12 a. Since the other squeegee 12 b is similarlyconstructed, only the construction of one squeegee 12 a is describedhere. It is to be noted that the squeegee 12 a (12 b) and thepressurizing member 28 are constructed so as to be able to adjust therelative mounting positions by being independently supported, asdescribed later.

In this case, the pressurizing member 28 is a rod body of a circularcross-section shape similar to that of the first embodiment. The planeof the squeegee 12 a and the center axis of the pressurizing member 28are supported parallel to each other in the lengthwise direction that isone example of the axial direction of the squeegee 12 a in the vicinityof the edge portion of the squeegee 12 a while being able to be movedhorizontally and vertically by a pressurizing member horizontal movementmechanism (referred to as a horizontal movement mechanism hereinafter)231 and a pressurizing member vertical movement mechanism (referred toas a vertical movement mechanism hereinafter) 232, which are mounted ona pair of brackets 30 arranged at both end portions of the rod body.

As the horizontal movement mechanism 231 and the vertical movementmechanism 232, for example, a combination of a thread shaft driven to beforwardly and reversely rotated by a motor and a nut meshed with thethread shaft, a well-known movement mechanism such as a solenoid capableof performing positional control with excellent accuracy, or the likecan be used. More specifically, for example, the horizontal movementmechanism 231 is constituted of a thread shaft 231 b driven to beforwardly and reversely rotated by a motor 231 a and a nut member 231 cmeshed with the thread shaft 231 b with a motor 232 a of the verticalmovement mechanism 232 fixed to the nut member 231 c. The verticalmovement mechanism 232 is constituted of a thread shaft 232 b driven tobe forwardly and reversely rotated by the motor 232 a and a nut member232 c meshed with the thread shaft 232 b and supporting the end portionof the pressurizing member 28.

Moreover, the squeegee 12 a is held by a holder cover 34 via a holder33, and the brackets 30 are fixed to the holder 33 by means of a boltand nut 35.

When the squeegee 12 a comes in contact with the printing mask 3, thepressurizing member 28 forms a narrow path 34 of a minute interval Sbetween the member and the surface 3 a of the printing mask 3. Theinterval S of this narrow path 34 is adjusted within a range of about 1mm to 3 mm by controlling the vertical movement mechanism 232.

Moreover, the pressurizing member 28 forms a flow path 36 of an intervalT, which becomes the flow path of the rolling solder paste during thesolder paste printing between the member and the squeegee 12 a (12 b).The interval T of this flow path 36 is also adjusted within a range ofabout 1 mm to 3 mm by controlling the horizontal movement mechanism 231.

By providing the pressurizing member 28 that can adjust the intervals Sand T of the above-mentioned narrow path 34 and flow path 36, as shownin FIG. 38A, the solder paste rolling during printing flows on the upperand lower sides of the pressurizing member 28. In particular, the solderpaste 7 on the lower side of the pressurizing member 28 comes tocirculate so as to pivot counterclockwise as indicated by arrow in thefigure by passing through the narrow path 34 located between the memberand the printing mask 3, thereafter passing through the flow path 36located between the squeegee 12 a and the pressurizing member 28, movingover or above the pressurizing member 28 to the right-hand side in FIG.4, and thereafter passing again through the narrow path 34. As a result,the filling pressure can be improved.

When the pressurizing member 28 is constructed of a round bar, thediameter d of the round bar is preferably about 2 to 10 mm and moreespecially be 5 to 7 mm. Moreover, the shape of the pressurizing member28 is not limited to the round bar, and those of various shapes of asemicircular cross-section shape, a wedge-like cross-section shape, orthe like can be utilized.

As shown in FIG. 38A, the pressurizing member 28 is provided so that theheight from the surface 3 a of the printing mask 3, i.e., the height hof the upper end surface of the pressurizing member 28 is lower than therolling height of the solder paste 7 during printing, i.e., the height Hof the upper surface of the solder paste 7 that is rolling, and thepressurizing member 28 is provided so as to sink in the rolling solderpaste 7 during printing.

By virtue of the formation of the narrow path 34 between thepressurizing member 28 and the printing mask 3, the solder paste thatpasses through the narrow path 34 during rolling comes to have a higherpressure than in the conventional case in accordance with the movementof the squeegees 12 a and 12 b. As a result, the solder paste 7 isproperly filled into the openings 4 of the printing mask 3, and ashortage of filling attributed to a shortage of filling pressure of thesolder paste, which has conventionally occurred, is eliminated.

Since a uniform pressure cannot be obtained in the lengthwise directionwhen the pressurizing member 28 warps when a high-pressure state occursin the narrow path 34, it is preferable to form the pressurizing member28 of a high-rigidity material that hardly causes warp. For example, thepressurizing member 28 is preferably formed of a metal, ceramic, or hardplastic.

FIG. 38B is a graph of the results of the measurement of the change inthe filling pressure of the solder paste 7 during high-speed squeegeeoperation at a squeegee speed of 200 mm/sec into the openings 4. In FIG.38B, the reference letter K represents the characteristics of thesqueegees 12 a and 12 b provided with the pressurizing members 28, andthe reference letter L represents the characteristics of theconventional squeegee provided with no pressurizing member 28. It is tobe noted that the measurement of this filling pressure was performedwith a pressure sensor 51 arranged on the back surface of the printingmask 3 and with an opening 4 a provided in the corresponding portion ofthe printing mask 3, as shown in FIG. 17.

Time t on the horizontal axis of the graph shown in FIG. 38B is the timefrom the start of the passing of the squeegee over the pressure sensor51 to the end of the passing, while the filling pressure P on thevertical axis is the pressure detected by the pressure sensor 51 via thesolder paste when the squeegee passes over the pressure sensor.

As is apparent from this graph, when the squeegee speed is increased,the conventional squeegee produces a pressure equal to or higher thanthe required pressure (refer to, for example, Pf in FIG. 38B) needed forthe filling only for a short time (refer to L in FIG. 38). On the otherhand, the squeegees 12 a and 12 b provided with the pressurizing members28 produce the required pressure needed for the filling for a long timeeven if the squeegee speed is increased (refer to K in FIG. 38B).

As described above, by virtue of the squeegees 12 a and 12 b providedwith the pressurizing members 28, a sufficient amount of solder paste 7can stably be filled into the openings 4 of the printing mask 3 even ifthe squeegee speed is increased.

The narrow path 34 preferably has a gap of about 1 mm to 3 mm generatedbetween the path and the printing mask 3 as described hereinabove, andit is only required to generate a gap of about 0.5 mm to 10 mm betweenthe path and the printing mask 3.

A control method for controlling the squeegee driving conditionsincluding the pressurizing member 28 will be described next on the basisof the solder paste filling pressure detected by the pressure sensor 51arranged on the lower surface of the printing mask 3, which is thecharacteristic construction of the solder paste printing apparatus 210of the fifth embodiment, with reference to the control block diagramshown in FIG. 39. The squeegee driving conditions are controlled by thecontrol unit 24 shown in FIG. 36 and FIG. 39.

The solder paste filling pressure detected by the pressure sensor 51 ispatterned as waveform data indicated by, for example, K in FIG. 38B by awaveform generating section 61 of the control unit 24 and transmitted toan operating section 62. The operating section 62 refers to a database64 that has preparatorily stored normal waveform data, or theinformation, which is the pressure waveform of the solder paste andbecomes a criterion of decision, and determines whether or not thewaveform of the measured filling pressure of the solder paste 7 isnormal by comparison.

Then, if the waveform of the measured filling pressure of the solderpaste 7 is normal as a result of this comparison, then the operatingsection 62 does not perform the following adjustment operation of thesqueegee driving conditions. If the waveform of the measured fillingpressure of the solder paste 7 is abnormal as a consequence ofcomparison and it is determined that the adjustment of the squeegeedriving conditions is needed, then operation signals are appropriatelyoutputted to a up-and-down driving driver 65 for vertically driving thesqueegee, a printing driving driver 66 for squeegee printing driving, ahorizontal movement driver 67 for the horizontal movement of thepressurizing member, and a vertical movement driver 68 for the verticalmovement of the pressurizing member, by which the squeegee up-and-downdrive devices 16 and 18, the printing drive device 26, the horizontalmovement mechanism 231, and the vertical movement mechanism 232 aredriven to perform the positional adjustment of the pressurizing member28, so that the desired filling pressure of the pressurizing member 28can be obtained. When it is determined whether or not the waveform ofthe measured filling pressure of the solder paste 7 is normal bycomparison referring to the database 64 that has preparatorily storedthe normal waveform data, it is also acceptable to preset the specifiedrange of tolerance for the normal waveform data and determine that thedata is normal when a deviation exists within the range of tolerance andthat the data is abnormal when the data exceeds the range of tolerance.

By this operation, the squeegee driving conditions of the applicationpressure of the squeegees 12 a and 12 b (a force that pressurizes thesqueegees 12 a and 12 b against the printing mask 3 in order to preventthe floating of the squeegees 12 a and 12 b), the squeegee speed V, thearrangement conditions of the pressurizing member 28 (the interval S ofthe narrow path 34 between the member and the printing mask 3 and theinterval T of the flow path 36 between the member and the squeegees 12 aand 12 b), and so on are adjusted. As one example of the adjustmentoperation of the squeegee driving conditions, the adjustment operationof the arrangement conditions of the pressurizing member 28 is firstperformed, and when the adjustment operation is insufficient, thesqueegee speed V is adjusted. As another example of the adjustmentoperation of the squeegee driving conditions, the arrangement conditionsof the pressurizing member 28 and the squeegee speed V are concurrentlyadjusted. As other parameters of these parameters for performing theadjustment of the squeegee driving conditions, there can be enumerated asqueegee angle a, a rolling height H depending on the amount of thesolder paste 7, the substantial diameter d of the pressurizing member28, the angle of inclination within the printing mask plane with respectto the direction in which the squeegees 12 a and 12 b move, and so on.

The database 64 preparatorily registers squeegee driving conditionadjustment information such as information of the extent of a change inthe filling pressure when the squeegee driving condition adjustmentparameters of the interval S,-the interval T, the squeegee speed V, andso on are changed and how the printing results are influenced by thechange of the parameters in combination in the form of, for example, atable or a graph or the like. With this arrangement, when it isdetermined that the waveform of the measured filling pressure of thesolder paste 7 is abnormal and the adjustment of the squeegee drivingconditions is needed, the operating section 62 finds the extent of thechange in the filling pressure on the basis of a difference between thewaveform of the detected filling pressure and the waveform of the normalfilling pressure registered in the database 64. On the basis of thefound results, the squeegee driving condition adjustment parameters ofthe interval S, the interval T, the squeegee speed V, and so on or thesqueegee driving condition adjustment parameters of any combination ofthe parameters are changed by referring to the squeegee drivingcondition adjustment information. As a result, the quantity of change ofeach parameter can promptly be set without needing the rule of thumb,and rapid and accurate adjustment work can be performed. As one concreteworking example, there is performed the adjustment for increasing theapplication pressure when the viscosity of the solder paste isincreased.

The solder paste printing operation by means of the solder pasteprinting apparatus 210 of the fifth embodiment constructed as above willbe described next with reference to the flowchart shown in FIG. 40.

First of all, the printed board 5 loaded from the printed boardconveying section 1A is positioned and layered on the back surface ofthe printing mask 3 whose surface is supplied with a prescribed amountof solder paste 7 by the table section 1B (step 11: hereinafter referredto as S11).

Next, in the case of the rightward printing, the rightward printingsqueegee 12 a is moved down by the squeegee up-and-down drive device 16as shown in FIG. 36. At this time, the edge portion of the squeegee 12 ais brought in contact with the surface 3 a of the printing mask 3 with aproper application pressure.

With this state maintained, the base plate 14 is moved rightward by theprinting drive device 26, and the squeegee 12 a is linearly moved in therightward direction (S12). By this operation, the filling of the solderpaste 7 into each opening 4 of the printing mask 3 and the scraping onthe surface 3 a of the printing mask 3 by the squeegee 12 a are startedas shown in FIG. 38A. At this time, the solder paste 7 on the lower sideof the pressurizing member 28 circulates so as to pass through thenarrow path 34 between the member and the printing mask 3, thereafterpass through the flow path 36 between the squeegee 12 a and thepressurizing member 28, and pass again through the narrow path 34, byrolling. By the passing of the solder paste 7 through this narrow path34, the filling pressure is increased, and the solder paste 7 issufficiently filled into each opening 4 of the printing mask 3 even ifthe squeegee speed is increased.

Next, the filling pressure of the solder paste 7 is detected by thepressure sensor 51 shown in FIG. 36 in accordance with the movement ofthe squeegee 12 a, and this detection result is outputted to the controlunit 24, by which the waveform data is generated in the waveformgenerating section 61 (S13). Then, the squeegee 12 a is moved to aspecified position, and the squeegee movement is ended (S14).

Subsequently, the printed board 5 is moved down by the table section 1Bso as to separate the printed board 5 from the printing mask 3 (S15).Although the pressure sensors 51 are provided at the two portions of theprinting start side and the printing end side of the printed board 5 inthe direction of the movement of the squeegee, the filling pressure isdetected by using only the pressure sensor 51 at the printing start sidein this case.

Next, it is determined whether or not the adjustment of the squeegeedriving conditions is required by the operating section 62 of thecontrol unit 24 by comparing the waveform detection result of thefilling pressure of the solder paste 7 with the optimum waveformregistered in the database 64 (S16).

In this case, when it is determined that the waveform detection resultcoincides with the optimum waveform and the adjustment of the squeegeedriving conditions is not needed by the operating section 62, theprinting of the solder paste 7 on the printed board 5 is ended in thisstate.

When it is determined that the waveform detection result does notcoincide with the optimum waveform and the adjustment of the squeegeedriving conditions is needed by the operating section 62, the method ofadjusting the squeegee driving conditions most appropriate for this caseis determined from the aforementioned comparison result by referring tothe squeegee driving condition adjustment information of the database64, and the squeegee driving conditions are adjusted (S17). Then, theprinted board 5 is replaced (S18), and the program flow returns again toS11. It is also acceptable to connect a display section 60 of a monitoror the like to the operating section 62 of the control unit 24 as shownin FIG. 39 and display the aforementioned comparison result or displaythe result only in the abnormal case.

Through the aforementioned processes, the solder paste 7 comes to beproperly printed on the printed board 5. When the printing conditionsare improper, the adjustment is repetitively performed until the properconditions are achieved, and finally the satisfactory printingconditions are set. As a board to be used for setting the satisfactoryprinting conditions (when the so-called teaching is performed), a boardfor test may be used besides the board to be produced.

The printing operation is similarly repetitively performed in theleftward printing manner when the previous printing operation has beenthe rightward printing and in the rightward printing manner when theprevious printing operation has been the leftward printing. By repeatingthe above-mentioned printing operation, the solder paste 7 can besuccessively continuously printed and applied on each land 6 of theprinted board 5 via the printing mask 3 under satisfactory printingconditions.

Moreover, since the printing conditions are fed back to the nextprinting process, it is possible to stably perform the repetitiveprinting consistently under satisfactory printing conditions and performhigh-quality solder paste printing.

Furthermore, the squeegee driving conditions are controlled on the basisof the pressure waveform that represents the change with the lapse oftime of the pressure of the solder paste. Therefore, an instantaneouschange in the pressure can be qualitatively and quantitatively perceivedmore precisely, and fine control can be performed, allowing more stablesatisfactory printing state to be maintained.

It is to be noted that solder paste printing apparatus 210 of the fifthembodiment is the type of the movement in both the rightward andleftward directions, and therefore, both the squeegees 12 a and 12 b areprovided. However, the solder paste printing apparatus may be the typeof the movement in either one of the directions, and in such a case, thesqueegee 12 a or the squeegee 12 b corresponding to the direction ofmovement is provided.

Although the fifth embodiment has the construction in which eachsqueegee is vertically moved, both the squeegees may be consistentlybrought in contact with the printing mask surface without verticallymoving during printing.

Another solder paste printing operation using the solder paste printingapparatus 210 of the fifth embodiment will be described next withreference to the flowchart shown in FIG. 41.

The printing operation shown in FIG. 41 executes feedback control inreal time during printing, and the operation procedure thereof will bedescribed below.

First of all, the printed board 5 is positioned similarly to S11 of FIG.40 (S21), and thereafter, the movement of the squeegee 12 a is started(S22). In accordance with the movement of this squeegee 12 a, thefilling pressure of the solder paste 7 is detected by the pressuresensor 51 provided on the this side of (short of) the printed boardprinting start end in the direction of the squeegee movement shown inFIG. 36, and this detection result is outputted to the control unit 24so as to generate waveform data in the waveform generating section 61(S23). Then, the operating section 62 of the control unit 24 determineswhether or not the adjustment of the squeegee driving conditions isneeded by comparing the generated waveform data with the optimumwaveform registered in the database 64 (S24).

In this case, when it is determined that the generated waveform datacoincides with the normal waveform data and the adjustment of thesqueegee driving conditions is not needed by the operating section 62,the squeegee is moved to the specified position to end the squeegeemovement (S25), and the printed board is made to separate from theprinting mask (S26).

When it is determined in S24 that the generated waveform data does notcoincide with the normal waveform data and the adjustment of thesqueegee driving conditions is needed by the operating section 62, themethod of adjusting the squeegee driving conditions most appropriate forthis case is determined on the basis of the aforementioned comparisonresult and the squeegee driving condition adjustment information of thedatabase 64, and then, the squeegee driving conditions are adjusted(S27) This adjustment is controlled so as to be performed in real timeduring the squeegee movement and completed before the squeegees 12 a and12 b reach the patterned openings 4 of the printing mask 3.

Then, in the state in which the squeegee driving conditions areadjusted, the detection of the filling pressure of the solder paste 7 isperformed again by the pressure sensor 51 provided on the rear side ofthe printed board printing end in the direction of squeegee movementafter the squeegees 12 a and 12 b have passed through the openings 4 ofthe printing mask 3, and this detection result is outputted to thecontrol unit 24 so as to generate a pressure waveform in the waveformgenerating section 61 (S28).

Then, the squeegee is moved to a specified position to end the squeegeemovement (S29), and the printed board 5 is made to separate from theprinting mask 3 (S30).

Next, it is determined whether or not the squeegee driving conditionsadjusted in S27 have been proper by comparing the waveform detectionresult of the solder paste filling pressure that has been detected bythe operating section 62 of the control unit 24 and generated in thewaveform generating section 61 with the optimum waveform registered inthe database 64. (S31)

In this case, when the adjustment of the squeegee driving conditions in.S27 is proper and the waveform detection result coincides with theoptimum waveform, the printing of the solder paste 7 on the printedboard 5 is ended in this state.

When it is determined that the adjustment of the squeegee drivingconditions in S27 has not yet been proper, the method of adjusting thesqueegee driving conditions most appropriate for this case is determinedagain on the basis of the aforementioned comparison result, and then,the squeegee driving conditions are adjusted (S32). Then, the printedboard 5 is replaced (S33), and the program flow returns again to S21.

Through the aforementioned processes, the printing of the solder paste 7on the printed board 5 is ended.

By performing the aforementioned solder paste printing operation, thepressure waveform of the application pressure is detected immediatelybefore performing the printing on the printed board, and the printing isperformed with the squeegee driving conditions properly adjusted beforethe pattern printing as the need arises. By this operation, the printingconditions can be changed in real time, and high-quality solder pasteprinting can promptly be achieved. Moreover, when the squeegee drivingconditions are adjusted, by detecting again the pressure waveform of theapplication pressure immediately after the printing on the printed boardso as to confirm whether or not the pressure waveform is the same as thespecified optimum waveform, the reliability of the driving conditionadjustment is improved, and the printing can be stably performed undersatisfactory squeegee driving conditions.

As described above, by adjusting the squeegee driving conditions in theearly stage by feeding back the printing result, a printed board in asatisfactory printing state can promptly simply be obtained.

Moreover, by performing the aforementioned printing operations, theadjustment work of the device during printing can be simplified, and theamount of work can be remarkably reduced. Therefore, the work efficiencyis improved, and stable printing can be continuously performed, enablingthe printing process appropriate for mass production to be performed.

Furthermore, by preparatorily registering the extent of change in thefilling pressure when each of the adjustment parameters of the intervalsS and T, the squeegee speed V, and so on is changed, how the printingresult is influenced by the change in the parameters in combination, andso on in the database, the quantity of change of each parameter canpromptly be set without needing the rule of thumb whatever fillingpressure waveform is detected, and this enables rapid and correctadjustment work.

According to the solder paste printing apparatus and printing method ofthe fifth embodiment of the present invention, by detecting the pressureof the solder paste increased by the pressurizing member provided in thevicinity of the edge portion of the squeegee by means of the pressuresensor and then controlling the squeegee driving conditions incorrespondence with the detection result of this pressure, the printingof the solder paste on the printed board can be correctly performedwithout causing the unfilled portion of the solder paste even if thesqueegee speed is fast, and this enables the easy increase in theprinting speed and the stable retainment of the satisfactory printingstate. For example, if the solder paste printing is continuouslyperformed, then the solder paste that has initially been supplied by aprescribed amount onto the printing mask becomes reduced. In this case,with regard to a relation between the amount of the solder paste and thefilling pressure waveform, no change in waveform is observed when theamount is, for example, 400 g to 700 g. However, the pressure becomesslightly reduced when the amount is 300 g, and a significant pressurereduction is observed when the amount is 200 g. In order not to performthe printing in the state in which the significant pressure reduction isobserved as a consequence of a shortage of solder paste as describedabove, it is possible to prevent the occurrence of defective printing byperforming trouble detection by the pressure sensor, informing theoperator of the trouble by means of the display section 60 of a monitoror the like and performing the squeegee driving conditions adjustmentbased on the squeegee driving condition adjustment information of thereplenishment of the solder paste and so on.

Also in the fifth embodiment, similarly to the foregoing embodiments, ifthe printing is repetitively performed with the conventionalconstruction, as shown in FIG. 26A, the solder paste 7 is protruded fromboth sides of the squeegee 12 a as indicated by 7A. This solder paste 7Aprotruded therefrom does not naturally return, and the operator collectsand puts back the paste at regular intervals of time or dispose of it.In contrast to this, by applying a pressure to the solder paste 7 withthe pressure generating member 28 arranged, the solder paste 7 rollsaround the pressure generating member 28 and comes to surround thepressurizing member 28. Therefore, even if the printing is repeated, asshown in FIG. 26B, a large amount of solder paste is not protrudeddissimilar to the conventional case. Therefore, the work of the operatorcan be reduced, and the productivity can be improved. Moreover,according to the solder paste printing apparatus of the fifthembodiment, there is provided the solder paste printing apparatus inwhich the squeegee moves in the printing direction on the surface of theprinting mask where the openings are formed so as to print and apply thesolder paste supplied onto the surface on the surface of the printedboard positioned on the back surface of the printing mask via theopenings, the apparatus being characterized by being provided with: thepressurizing member that is provided in the vicinity of the edge of thesqueegee and forms the narrow path between the member and the printingmask and the flow path between the member and the squeegee duringprinting, the pressure sensor that is provided within the range ofprinting on the back side of the printing mask, or the range of movementof the squeegee and detects the pressure of the solder paste applied viathe opening for pressure detection formed in the printing mask; and thecontrol means for controlling the driving conditions of the squeegee incorrespondence with the detection result of the pressure sensor.

In this solder paste printing apparatus, the pressure of the solderpaste that flows between the pressurizing member and the printing maskis increased by the movement of the squeegee during printing, and thesolder paste flows more downward by the increased pressure and filledinto the openings of the printing mask. The pressurizing member formsthe narrow path between the member and the mask surface, and therefore,the solder paste that flows between the pressurizing member and the masksurface maintains a high pressure for a long time. Then, by detectingthe pressure of the solder paste increased by the pressurizing memberprovided for this squeegee by means of the pressure sensor and thencontrolling the driving conditions of the squeegee by the control meansin correspondence with the detection result of the pressure by thepressure sensor, the printing of the solder paste on the printed boardcan correctly be performed without causing the unfilled portion of thesolder paste even if the squeegee speed is fast, and this enables theeasy increase in the printing speed and the stable retainment of thesatisfactory printing state.

Moreover, in the solder paste printing apparatus of the fifthembodiment, the control means can also execute control on the basis ofthe pressure waveform that represents the change with the lapse of timeof the pressure of the solder paste detected by the pressure sensor.

In the solder paste printing apparatus described above, by controllingthe squeegee driving conditions on the basis of the pressure waveformthat represents the change with the lapse of time of the pressure of thesolder paste detected by the pressure sensor, an instantaneous change inthe pressure can be more precisely perceived, and this enables theexecution of fine control and the retainment of more stabilizedsatisfactory printing state.

Moreover, in the solder paste printing apparatus of the fifthembodiment, the control means is provided with the database in which thepressure waveform of the solder paste is registered, and the squeegeedriving conditions can also be controlled by comparing the pressurewaveform detected by the pressure sensor with the solder paste pressurewaveform, which becomes a criterion of decision registered in thedatabase.

In the solder paste printing apparatus described above, by controllingthe squeegee driving conditions through the comparison of the pressurewaveform detected by the pressure sensor with the optimum pressurewaveform registered in the database, the control can easily be achievedon the basis of the qualitative and quantitative differences of thepressure waveform, and therefore, the more proper adjustment of thesqueegee driving conditions can be performed.

Furthermore, the solder paste printing apparatus of the fifth embodimentis provided with the squeegee up-and-down drive device for changing therelative position in the up-and-down direction of the squeegee withrespect to the printing mask and is also able to adjust the relativeposition by driving the squeegee up-and-down drive device by the controlmeans.

In the solder paste printing apparatus described above, by adjusting therelative position in the up-and-down direction of the squeegee withrespect to the printing mask, the pressure of the solder pastepressurized by the squeegee can be increased or decreased, and thepressure of the solder paste can properly be controlled.

Moreover, the solder paste printing apparatus of the fifth embodiment isprovided with the printing drive device that moves the squeegee in theprinting direction and is also able to adjust the travel speed of thesqueegee in the printing direction by driving the printing drive deviceby the control means.

In the solder paste printing apparatus described above, by adjusting thesqueegee speed, that is, the squeegee travel speed in the printingdirection, the pressure applied to the solder paste can be increased anddecreased according to the magnitude of the travel speed, and thepressure of the solder paste can properly be controlled.

Moreover, the solder paste printing apparatus of the fifth embodiment isprovided with the pressurizing member horizontal movement mechanism forchanging the relative position of the pressurizing member with respectto the squeegee and is also able to adjust the relative position of thepressurizing member by driving the pressurizing member horizontalmovement mechanism by the control means.

In the solder paste printing apparatus described above, by adjusting therelative position of the pressurizing member with respect to thesqueegee, the fluid resistance when the solder paste subjected toconvection passes through the flow path between the pressurizing memberand the squeegee increases or decreases, and the pressure of the solderpaste can properly be controlled.

Moreover, the solder paste printing apparatus of the fifth embodiment isprovided with the pressurizing member vertical movement mechanism forchanging the relative position of the pressurizing member with respectto the printing mask and is also able to adjust the relative position ofthe pressurizing member by driving the pressurizing member verticalmovement mechanism by the control means.

In this solder paste printing apparatus, by adjusting the relativeposition of the pressurizing member with respect to the printing mask,the fluid pressure when the solder paste subjected to convection passesthrough the narrow path between the pressurizing member and the printingmask increases or decreases, and the pressure of the solder paste canproperly be controlled.

Moreover, the solder paste printing apparatus of the fifth embodiment isprovided with the pressure sensor arranged on this side of the printingstart end of the circuit board and is also able to detect the solderpaste pressure before the start of the printing of the circuit board.

In the solder paste printing apparatus described above, by providing thepressure sensor on this side of the printing start end of the circuitboard and detecting the solder paste pressure before the start of theprinting of the circuit board, the control of the squeegee drivingconditions can be completed by the start of the pattern printing on thecircuit board, and this enables the execution of the printing under theoptimum driving conditions in real time.

Moreover, according to the solder paste printing method of the fifthembodiment for printing and applying the solder paste on the surface ofthe printing mask onto the printed board positioned on the back surfaceof the printing mask via the openings by moving the squeegee in theprinting direction on the surface of the printing mask where theopenings are formed, it is possible to increase the pressure of thesolder paste that flows between the member and the printing mask by thepressurizing member provided in the vicinity of the edge portion of thesqueegee, detect the increased pressure of the solder paste, and controlthe printing conditions of the squeegee by comparing the detectedpressure with the preparatorily registered specified pressure.

According to the solder paste printing method described above, thepressure applied to the solder paste is detected, and the detectionresult of this pressure is compared with the preparatorily registeredspecified pressure. When the detection result of the pressure isdifferent from the normal pressure, by executing control so that thedriving conditions of the squeegee are changed and the desired pressureis achieved, the solder paste can correctly be printed on the printedboard without causing the unfilled portion of the solder paste even ifthe squeegee speed is fast. This enables the easy increase in theprinting speed and the stable retainment of the satisfactory printingstate.

Moreover, according to the solder paste printing method of the fifthembodiment, it is also possible to measure the pressure of the solderpaste before the start of the pattern printing of the circuit board andcomplete the control of the squeegee driving conditions before the startof the pattern printing.

According to the solder paste printing method described above, bymeasuring the pressure of the solder paste before the start of thepattern printing of the circuit board and completing the control of thesqueegee driving conditions before the start of the pattern printing,the pattern can be printed in real time under the satisfactory drivingconditions, and high-quality solder paste printing can promptly beachieved.

(Sixth Embodiment)

The sixth embodiment of the present invention is related to a screenprinting method and a screen printing apparatus for printing a printingpaste on a board via a screen and is more precisely intended to reducethe printing time.

A conventional issue will be first described before describing the sixthembodiment.

Referring to FIG. 49, conventionally, Japanese Patent No. 2850150describes a screen printing machine 390, which fixes a printed board 393on a stage 392 that can horizontally advance and retreat and verticallymove with respect to a screen form plate 391 and prints a printing pasteon the printed board 393 via the screen form plate 391 by a squeegeehead, or a printing head 394.

In the screen printing machine 390, the positional alignment of theprinted board 393 with the screen form plate 391 is performed byindependently detecting positioning marks 395 respectively provided onthe printed board 393 and the screen form plate 391 by means of arecognition camera 396 and moving the stage 392 and the screen formplate 391 in the horizontal and vertical directions, respectively, onthe basis of the detection.

The loading and unloading of the printed board 393 on the stage 392 areperformed by a loader and an unloader (which are not shown),respectively. The loader and the unloader are driven by a common-usedriving mechanism (not shown) mounted on the stage 392.

That is, the loader is operated by the driving of the driving mechanismby being connected to the driving mechanism of the stage 392horizontally moved to the right-hand end of a rail 397 in FIG. 49 whenthe printed board 393 is loaded. The unloader is operated by the drivingof the driving mechanism by being connected to the driving mechanism ofthe stage 392 horizontally moved to the left-hand end of the rail 397 inFIG. 49 when the printed board 393 is unloaded.

Referring to FIG. 50, Unexamined Japanese Patent Publication No.10-44370 describes a screen printing machine 400, which is provided witha first imaging device 402 for imaging a position recognition mark (notshown) preparatorily attached to a board 401 and a second imaging device404 for imaging a position recognition mark (not shown) preparatorilyattached to a screen 403.

The screen printing machine 400 performs the positional alignment of theboard 401 with the screen 403 by moving a board support table 405 and ascreen support device 406 each by a required amount in the horizontal orvertical direction on the basis of the deviation of the positionalinformation obtained by the imaging devices.

The first imaging device 402 is provided between the board support table405 placed on a base 407 and the screen support device 406 that supportsthe screen 403 and images the positional recognition mark of the board401 placed on the board support table 405 by means of a camera 408.

The second imaging device 404 is provided above the screen supportdevice 406 and images the positional recognition mark of the screen 403supported by the screen support device 406 by means of a camera 409.

Furthermore, referring to FIG. 51, Unexamined Japanese PatentPublication No. 7-329276 describes a screen printing apparatus 410,which supports a Y-table 412 movably in the lateral direction in FIG. 51on an X-table 411 provided movably in the direction perpendicular to thesheet plane of FIG. 51 on a base (not shown) and supports first andsecond elevation plates 413 and 414 on the Y-table 412 while being ableto move up and down in the vertical direction in FIG. 51.

The X-table 411 is moved by an X-motor 415. The Y-table 412 is moved bya Y-motor .416.

The first elevation plate 413 is supported in the vertical directionwhile being able to move up and down in FIG. 51 by meshing a nut 419with a pair of feed screws 418 interlocked via a timing belt 417. Thefirst elevation plate 413 is moved up and down in the vertical directionin FIG. 51 with respect to the Y-table 412 along the feed screw 418 by ascrewing action generated between the feed screw 418 and the nut 419according to the rotation of the feed screw 418 in accordance with therotation of a first motor 420.

The second elevation plate 414 is supported while being able to move upand down via bearings 422 by a pair of elevation guides 421 providedupright on the first elevation plate 413. The second elevation plate 414is moved up and down in the vertical direction in FIG. 51 with respectto the first elevation plate 413 along the elevation guide 421 by ascrewing action generated between a feed screw 424 and a nut 425according to the rotation of the feed screw 424 in accordance with therotation of a second motor 423. A suction block 426 is provided on thesecond elevation plate 414, and a printed board 427 is sucked onto thesuction block 426.

In the screen printing machine 390 shown in FIG. 49 described in theJapanese Patent No. 2850150, the loader and the unloader are driven bythe common-use drive mechanism mounted on the stage 392, and the loadingand unloading of the printed board 393 to and from the stage 392 areperformed separately at the right-hand end portion and the left-hand endportion of the rail 397 in FIG. 49. Therefore, the trouble of thecontact of the printed board 393 to be loaded with the printed board 393to be unloaded does not occur.

However, there has been an issue that much time is required forconnecting the driving mechanism of the stage 392 to the loader or theunloader or release the connection, and the time required for replacingthe printed board 393 is increased. There has also been another issuethat the installation area in the horizontal plane of the device islarge since the stage 392 moves between the loader and the screen 391and the position recognizing section of the recognition camera 396 islocated between the loader and the screen 391, resulting in difficultiesin compacting the device.

Moreover, in the screen printing machine 400 described in UnexaminedJapanese Patent Publication No 10-44370 shown in FIG. 50, the positionrecognition marks of the board 401 and the screen 403 are respectivelyimaged by the separate imaging devices arranged in the upper and lowerportions of FIG. 50. Accordingly, there is no need for moving the board401 into, for example, a position where the board does not overlap thescreen 403 vertically when the board 401 is imaged. Therefore, theinstallation area in the horizontal plane of the device can be reduced.

However, there has been an issue that, if a slight deviation of theoptical axis exists in the reference position of each imaging device,the deviation becomes an extremely serious issue in improving thedetection accuracy, and the accurate detection position cannot beobtained. Moreover, there is the operation of moving the board and thescreen in the vertical direction from the mark detection position in thepractical positional alignment even if the marks are accurately detectedby the imaging devices, and therefore, the positional alignment cannotaccurately be performed when the axis slightly deviates from thevertical direction. Furthermore, there has been an issue that theworking hours have become long since time is required for making theimaging device advance and retreat.

Furthermore, in the screen printing apparatus 410 of. UnexaminedJapanese Patent Publication No. 7-329276 shown in FIG. 51, the mechanismfor moving up and down the first elevation plate 413 and the mechanismfor moving up and down the second elevation plate 414 are separatemechanisms, and the suction block 426 of the printed board the secondelevation plate 414, and its elevation mechanism are placed on the firstelevation plate 413.

For the above reasons, there has been an issue is that the inertia inthe elevation operation is increased as a consequence of the increasedweight, and hunting (oscillation) significantly appears. There has beenan issue that, if the hunting significantly appears, it is required towait until the hunting disappears, and the time required to thecompletion of the printing becomes long. There has also been an issuethat errors due to the two elevation mechanisms are multiplied, leadingto a low positional alignment accuracy.

The object of the sixth embodiment of the present invention is toprovide a screen printing method and a screen printing apparatus capableof reducing the time required for the replacement of the board and therecognition of the reference position marks by the recognition camerasand so on, thus reducing the printing time, obtaining high positionalalignment accuracy, performing stable printing even when the printingspeed is increased for time reduction, achieving high-quality solderpaste printing with high productivity, and further compacting theapparatus.

FIG. 42 is a schematic plan view showing the solder paste printing,i.e., the screen printing apparatus of the sixth embodiment of thepresent invention. FIG. 43 is a view of the inside of the screenprinting apparatus viewed from the front. FIG. 44 is a front view of thescreen printing apparatus with its cover open. FIG. 45 is a right sideview of the screen printing apparatus. FIG. 46 is a front view showingthe table section horizontal movement mechanism, the support baseelevation mechanism, and the movable frame elevation mechanism of thescreen printing apparatus of FIG. 42. FIG. 47A is a right side view ofFIG. 46.

Referring to FIG. 42 through FIG. 47B, the screen printing apparatus 310of the sixth embodiment of the present invention prints a printing paste(not shown) as described in, for example, the foregoing embodiment bymeans of a squeegee head, i.e., a printing head section 370 via aprinting mask, i.e., a screen 312 supported by a screen table section360 on a board 311 supported by a support base 340. The support base 340is supported roughly in the vertical direction (direction of an arrow Zin FIG. 46) while being able to be moved up and down by a movable frame346 that can move up and down roughly in the vertical direction(direction of the arrow Z in FIG. 46) with respect to the table section320.

The table section 320 is supported by an apparatus frame 313 while beingable to move in the horizontal direction via a table section guide 321.The table section 320 is horizontally moved by a table sectionhorizontal movement mechanism 322 in a direction (direction of an arrowY of FIG. 42, a direction perpendicular to the sheet plane of FIG. 46)roughly perpendicular to a board loading and unloading direction X1(direction of an arrow X1 in the direction of an arrow X in FIG. 42) tothe support base 340. It is to be noted that the horizon mentionedwithin this specification and the scope of the claims is not alwayslimited to the direction along the horizontal line but includes adirection inclined by a specified angle with respect to the horizontalline, and the direction may alternatively be referred to as a sidewisedirection.

Referring to FIG. 46, FIG. 47A, and FIG. 47B, the table sectionhorizontal movement mechanism 322 includes a ball thread mechanismconstructed of a ball thread shaft 323 that has an outer peripheralsurface on which a ball thread is formed and a ball thread nut 324 thatis provided on the lower surface of the table section 320 and is meshedwith the ball thread shaft 323, and a table section horizontal movementmotor 325 for forwardly and reversely rotating the ball thread shaft 323of the ball thread mechanism.

The table section horizontal movement mechanism 322 forwardly andreversely rotates the ball thread shaft 323 of the ball thread mechanismby means of the table section horizontal movement motor 325, therebygenerating a screwing action between the ball thread shaft 323 and theball thread nut 324 and making the table section 320 horizontallyadvance and retreat in the direction of the arrow Y along the tablesection guide 321.

Referring to FIG. 42 and FIG. 43, a board loader 330 is providedproximately to the right-hand side of the table section 320 in FIG. 42with interposition of a minimum gap necessary for the transfer of theboard 311 between the loader and the support bases 340. The board loader330 loads the board 311 before being printed (hereinafter referred to asa pre-printing board 311) in the board loading and unloading directionX1 onto the support base 340.

A board unloader 331 is provided proximately to the left-hand side ofthe table section 320 in FIG. 42 with interposition of a minimum gapnecessary for the transfer of the board 311 between the unloader and thesupport bases 340. The board unloader 331 unloads the board 311 afterbeing printed (hereinafter referred to as an already-printed board 311)located on the support base 340 in the board loading and unloadingdirection X1.

The board loader 330 and the board unloader 331 are constructed of anidentical structure, and therefore, the detail of the board loader 330is shown as a representative in FIG. 58. The board loader 330 isconstructed of a pair of conveyance belts 330 b for conveying both sidesof the board 311 and a pair of drive motors 330 d for driving the pairof conveyance belts 330 b so as to forwardly and reversely rotate thebelts in synchronism. By driving the pair of drive motors 330 d so as tosynchronously rotate the motors under the control of a control unit 399,the pair of conveyance belts 330 b is synchronously driven to move theboard 311 in a specified direction. Reference numeral 330 t denotes awidthwise adjustment drive motor for varying the interval between thepair of conveyance belts 330 b, and 330 s denotes a drive shaft formoving either one of the pair of conveyance belts 330 b in a directionin which the belt moves close to or apart from the other one by theforward and reverse rotation drive of the widthwise adjustment drivemotor 330 t. The board unloader 331 has a construction similar to thatof the board loader 330.

As shown in FIG. 46, FIG. 47A, and FIG. 47B, the support base 340 issupported so as to be able to move up and down in the direction of thearrow Z via four support base elevation guides 341 by four guide shafts327 that are inserted so as to be able to move up and down in thedirection of the arrow Z in the four guide shafts 326 of the tablesection 320. The support base 340 can be moved up and down in thedirection of the arrow Z along the four guide shafts 327 via foursupport base elevation guides 341 by a support base elevation mechanism342.

The support base elevation mechanism 342 is provided with: a ball threadmechanism constructed of a ball thread shaft 343 on the peripheralsurface of which a ball thread is formed and a ball thread nut 344 thatis provided on the support base 340 and meshed with the ball threadshaft 343; and a support base elevation motor 345 for forwardly andreversely rotating the ball thread shaft 343 of the ball threadmechanism, the mechanism and the motor being provided on the movableframe 346.

The support base elevation mechanism 342 forwardly and reversely rotatesthe ball thread shaft 343 of the ball thread mechanism by means of thesupport base elevation motor 345, thereby generating a screwing actionbetween the ball thread shaft 343 and the ball thread nut 344 and movingup and down the support base 340 fixed to the support base elevationguides 341 in the direction of the arrow Z along the guide shafts 327with respect to the movable frame 346.

The support base elevation mechanism 342 supports by the support base340 the board 311 loaded into the specified board support position onthe support base 340 by the board loader 330 and a board conveyancemechanism 351 described later by moving up the support base 340 in thedirection of the arrow Z with respect to the movable frame 346.

The movable frame 346 has both right-hand and left-hand end portionsshown in FIG. 46 fixed to the lower end portions of the guide shafts 327in FIG. 46. The movable frame 346 is moved up and down in the directionof the arrow Z between a specified position of height where the printingon the board 311 located on the support base 340 is performed(hereinafter referred to as a raised position) and a specified positionof height where the loading and unloading of the board 311 on thesupport base 340 are performed (hereinafter referred to as a loweredposition) in accordance with the vertical movement in the direction ofthe arrow Z of the guide shafts 327 with respect to the elevation guides326 by a movable frame elevation mechanism 347.

As shown in FIG. 47A, the movable frame elevation mechanism 347 isprovided with: a ball thread mechanism constructed of a ball threadshaft 343 commonly used for the support base elevation mechanism 342 anda ball thread nut 348 that is meshed with the ball thread shaft 343 androtatably supported by the table section 320; and a movable frameelevation motor 349 for forwardly and reversely rotating the ball threadnut 348 of the ball thread mechanism, the mechanism and the motor beingprovided on the table section 320.

The movable frame elevation motor 349 forwardly and reversely rotatesthe ball thread nut 348 of the ball thread mechanism via a timing pulley348 a fixed to the ball thread nut 348 and a timing belt 350 woundaround the timing pulley 348 a.

The movable frame elevation mechanism 347 forwardly and reverselyrotates the ball thread nut 348 of the ball thread mechanism by means ofthe movable frame elevation motor 349, thereby generating a screwingaction between the ball thread shaft 343 and the ball thread nut 348. Bythis operation, the movable frame elevation mechanism 347 moves up anddown the ball thread shaft 343 in the direction of the arrow Z withrespect to the table section 320 and moves up and down the movable frame346 in the direction of the arrow Z between the raised position and thelowered position together with the guide shafts 327 with respect to thetable section 320.

As described hereinabove, each of the ball thread shaft 343 and theguide shafts 327 of the ball thread mechanism is commonly used by thesupport base elevation mechanism 342 and the movable frame elevationmechanism 347.

That is, the ball thread shaft 343 generates a screwing action betweenthe shaft and the ball thread nut 344 of the support base elevationmechanism 342 by being rotated forwardly and reversely in accordancewith the operation of the support base elevation motor 345, thus movingthe support base 340 up and down along the guide shafts 327 via thesupport base elevation guides 341.

The ball thread shaft 343 generates a screwing action between the shaftand the ball thread nut 348 by the forward and reverse rotation of theball thread nut 348 of the movable frame elevation mechanism 347 inaccordance with the operation of the movable frame elevation motor 349,thus moving the movable frame 346 up and down together with the guideshafts 327.

The support base 340 supports the board 311 on a plurality of supportpins 340 a that are projecting in specified board support positions onthe upper surface in FIG. 46 in accordance with the elevating operationof the support base elevation mechanism 342.

Referring to FIG. 42 through FIG. 47B, the printed board 311 supportedon the support pins 340 a of the support base 340 is loaded onto thesupport base 340 by the board loader 330, thereafter conveyed on thesupport base 340 by the board conveyance mechanism 351, stopped at aspecified board support position by a board stopper 352 and positionedthereat by a board regulation mechanism 355.

The board conveyance mechanism 351 is constructed of a belt conveyer andprovided above the table section 320 of the apparatus frame 313. Asshown in FIG. 59, the belt conveyer of the board conveyance mechanism351 is constructed of a pair of conveyance belts 308 b for conveyingboth sides of the board 311 and a pair of drive motors 308 for drivingthe pair of conveyance belts 308 b so as to forwardly and reverselyrotate the belts in synchronism. By driving the pair of drive motors 308so as to synchronously rotate the motors under the control of thecontrol unit 399, the pair of conveyance belts 308 b is synchronouslydriven to move the board 311 in a specified direction. Reference numeral309 denotes a widthwise adjustment drive motor for varying the intervalbetween the pair of conveyance belts 308 b, and 308 c denotes a driveshaft for moving either one of the pair of conveyance belts 308 b in adirection in which the belt moves close to or apart from the other oneby the forward and reverse rotation drive of the widthwise adjustmentdrive motor 309. The board conveyance mechanism 351 conveys the board311 loaded on the support base 340 by the board loader 330 to aspecified board support position.

As shown in FIG. 57, the board stopper 352 is provided so as to be ableto advance and retreat by the driving of a drive device 352 d of an aircylinder for the board stopper or the like into the board supportposition of the support base 340 and stops the board 311 in the boardsupport position by being engaged with the fore end portion of the board311 conveyed by the board conveyance mechanism 351 in a state in whichthe stopper advances.

As shown in FIG. 57, a board detection sensor 353 for detecting theboard 311 is provided for the board stopper 352 and detects the presenceor absence of the board 311 in the board support position of the supportbase 340.

As shown in FIG. 57, a cushioning member 354 is provided on the surfacethat belongs to the board stopper 352 and is engaged with the board 311.The cushioning member 354 attenuates the inertial force of the board 311to be loaded and stops the vibration of the board 311 in an extremelyshort time (within, for example, 0.1 seconds).

As shown in FIG. 47A and FIG. 47B, the board regulation mechanism 355has: a regulating member 355 a that has a roughly C-figured leading endand is provided so as to be able to advance and retreat in the directionof the arrow Y in the board support position of the support base 340;and an air cylinder 355 d for making the regulating member 355 a advanceand retreat between a position regulating position (position indicatedby the solid lines in FIG. 47B) for performing the positional regulationof the board 311 by inserting the right-hand end portion of the board311 into the leading end of the regulating member 355 a in FIG. 47A,pressurizing the board 311 in the leftward direction and pressurizingthe left-hand end portion of the board 311 against a fixed portion 355 eand a retreated position (indicated by the chain lines in FIG. 47B)where the cylinder is retreated in the rightward direction so as not tocome in contact with the board 311. The board regulation mechanism 355positions the board 311 stopped by the board stopper 352 on the supportbase 340 by pressurizing the board against a specified side by makingthe regulating member 355 a advance onto the support base 340.

As shown in FIG. 42, the screen table section 360 is arranged above thesupport base 340 of the apparatus frame 313 and holds the screen 312 bymeans of at least four clamps 364 to hold the screen in a roughlyhorizontal state. The screen table section 360 is made to horizontallyadvance and retreat in the direction of the arrow X by the screen tablesection horizontal movement mechanism 361 and rotated forwardly andreversely by a screen table section rotation mechanism 362 in ahorizontal plane roughly parallel to the board 311 supported on thesupport base 340. That is, as shown in FIG. 43 and FIG. 56, in thescreen table section rotation mechanism 362, a θ-table 360θ having apair of sliders 362 h that slides on a pair of curved guide rails 362 gfixed on an X-table 360X that can move in the X-direction on theapparatus frame 313 is arranged, and a θ-table rotating drive device 362d of a motor for rotatively driving the θ-table 360θ or the like isprovided. At least four clamps 364 are arranged on the θ-table 360θ, andthe screen 312 is gripped by at least four clamps 364 on the θ-table360θ. Therefore, by driving the θ-table rotating drive device 362 d ofthe screen table section rotation mechanism 362 so as to rotate theθ-table rotating drive device forwardly and reversely under the controlof the control unit 399, a pair of sliders 362 h and 362 h located onboth sides of the θ-table 360θ advance and retreat along the curvedguide rails 362 g located on both sides of the X-table 360X. By thisoperation, the θ-table 360θ can rotate forwardly and reversely withrespect to the X-table 360X within a specified angular range around thecenter axis of the support base 340.

Referring to FIG. 42 and FIG. 43, the screen table section horizontalmovement mechanism 361 is provided with: a ball thread mechanism (notshown) constructed of a ball thread shaft (not shown) on the outerperipheral surface of which a ball thread is formed and a ball threadnut (not shown) that is provided on the screen table section 360 andmeshed with the ball thread shaft; and a screen table section horizontalmovement motor 363 for forwardly and reversely rotating the ball threadshaft of the ball thread mechanism.

The screen table section horizontal movement mechanism 361 generates ascrewing action between the ball thread shaft and the ball thread nut byforwardly and reversely rotating the ball thread shaft of the ballthread mechanism by means of the screen table section horizontalmovement motor 363, thereby making the X-table 360X on which the θ-table360θ, that is gripping the screen 312 in the screen table section 360 isplaced, horizontally advance and retreat in the direction of the arrow Xwith respect to the apparatus frame 313.

Referring to FIG. 42 through FIG. 45, the printing head section 370 isarranged above the screen table section 360 in the apparatus frame 313,and provided with a printing head frame 371 and a printing squeegee 372.The printing head section 370 is made to horizontally advance andretreat in the direction of the arrow Y by a printing head sectionhorizontal movement mechanism 373.

As shown in detail in FIG. 55, the printing head section horizontalmovement mechanism 373 is provided with: a ball thread shaft mechanismconstructed of a ball thread shaft 374 on the outer peripheral surfaceof which a ball thread is formed and a ball thread nut 375 that isprovided on the printing head frame 371 and meshed with the ball threadshaft 374; and a printing head section horizontal movement motor 376 forforwardly and reversely rotating the ball thread shaft 374 of the ballthread mechanism.

The printing head section horizontal movement mechanism 373 generates ascrewing action between the ball thread shaft 374 and the ball threadnut 375 by forwardly and reversely rotating the ball thread shaft 374 ofthe ball thread mechanism by means of the printing head sectionhorizontal movement motor 376, thereby making the printing head frame371 and the printing head section 370 horizontally advance and retreatin the direction of the arrow Y.

As also shown in FIG. 52 and FIG. 53, the printing head section 370prints a printing paste on the board 311 via the screen 312 bysqueegeeing the printing paste by means of the printing squeegee 372 onthe screen 312 supported by the screen table section 360 in accordancewith the horizontal movement in the direction of the arrow Y of theprinting head section horizontal movement mechanism 373. The printingsqueegee 372 corresponds to the squeegees 12 a and 12 b of the foregoingembodiments and is able to independently move up and down between thestandby position where the lower end of the squeegee is located abovethe screen 312 by the up-and-down drive devices 16 and 18 that arearranged on the printing head frame 371 and covered with a head cover371 h and the operating position where the lower end of the squeegee isput in contact with the screen 312, similarly to the foregoingembodiments.

A recognition camera 380 is provided horizontally movably in thedirection of the arrow X and in the direction of the arrow Y and is ableto recognize the reference position marks (refer to, for example, 1005Aand 1005B of the board 5 in FIG. 32 and 1003A and 1003B of the screen 3in FIG. 32 and FIG. 33) preparatorily given to the board 311 and thescreen 312.

As shown in FIG. 55, the horizontal movement mechanism in the directionof the arrow X of the recognition camera 380 is provided with: a ballthread mechanism constructed of a camera X-shaft (i.e., X-directionrotary shaft) 382 that is provided on a recognition camera frame 381 cand is a ball thread shaft and a ball thread nut that is provided on amovable bracket 380 f of the recognition camera frame 381 c and meshedwith the camera X-shaft 382; and a camera X-shaft movement motor 381 forforwardly and reversely rotating the camera X-shaft 382 of the ballthread mechanism. Therefore, by a screwing action in accordance with theforward and reverse rotation of the camera X-shaft 382 by the X-shaftmovement motor 381, the movable bracket 380 f to which the ball threadnut meshed with the camera X-shaft 382 is fixed is moved to advance andretreat in the direction of the arrow X. A mounting bracket 380 c towhich the recognition camera 380 is fixed as shown in FIG. 54 is fixedto the movable bracket 380 f.

As shown in FIG. 55, the horizontal movement mechanism in the directionof the arrow Y of the recognition camera 380 is provided with: a ballthread mechanism constructed of a camera Y-shaft (i.e., Y-directionrotary shaft) 384 that is a ball thread shaft and a ball thread nut 381g that is provided on the recognition camera frame 381 c and meshed withthe camera Y-shaft 384; and a camera Y-shaft movement motor 383 forforwardly and reversely rotating the camera Y-shaft 384 of the ballthread mechanism. Therefore, by a screwing action in accordance with theforward and reverse rotation of the camera Y-shaft 384 by the cameraY-shaft movement motor 383, the recognition camera frame 381 c is movedto advance and retreat in the direction of the arrow Y.

That is, in a state in which the table section 320 is moved tohorizontally advance and retreat into a specified position (positionindicated by the two-dot chain lines in FIG. 42, hereinafter referred toas a recognition position) deviating from the position just below thescreen 312 by the table section horizontal movement mechanism 322, therecognition camera 380 performs the recognition of the referenceposition mark (refer to 1005A and 1005B of the board 5 in FIG. 32)formed in at least one place or, for example, two places of the board311 in accordance with the horizontal movement in the direction of thearrow X and the horizontal movement of the table section 320 in thedirection of the arrow Y by the table section horizontal movementmechanism 322. That is, the camera moves to a position above eachreference position mark (refer to 1005A and 1005B of the board 5 in FIG.32) of the board 311, and thereafter once stops to perform therecognizing operation.

The recognition camera 380 also performs the recognition of thereference position mark (refer to 1003A and 1003B of the screen 3 inFIG. 32 and FIG. 33) formed in at least one place or, for example, twoplaces of the screen 312 in accordance with the movement in thedirection of the arrow X and in the direction of the arrow Y. That is,the camera moves to a position above each reference position mark (referto 1003A and 1003B of the screen 3 in FIG. 32 and FIG. 33) of the screen312, and thereafter once stops to perform the recognizing operation.

The aforementioned constituent elements are each controlled by thecontrol unit (control means) 399 as shown in FIG. 60 and FIG. 61.

FIG. 60 is a timing chart showing the operation as a more concreteexample. The board detection sensor (entrance) in FIG. 60 means theoperation of a board detection sensor 306 in on the entrance side of theboard loader 330. The board detection sensor (unloader exit) means theoperation of a board detection sensor arranged on the exit or entrance(see FIG. 61) side of the unloader 331. The loader belt means theoperation of a conveyance belt drive motor 330 d of the board loader330. The unloader belt means the operation of a pair of conveyance beltdrive motors 331 d of the board discharging loader (unloader) 331. Thetable belt means the operation of a pair of conveyance belt drive motors308 of the board conveyance mechanism 351. A board stopper (cylinder)means the operation of a board stopper air cylinder 352 d. The boarddetection sensor (table) means the operation of the board detectionsensor 353. The table shaft means the operation of a table sectionhorizontal movement motor 325 of the table section horizontal movementmechanism 322. The mark-1 movement of the table shaft means theoperation of the table section horizontal movement motor 325 formovement to either one of the two positional alignment marks 1005A and1005B of the printed board 5 in the table section. Two mark-2 movementof the table shaft means the operation of the table section horizontalmovement motor 325 for movement to the other one of the two positionalalignment marks 1005A and 1005B of the printed board 5 in the tablesection. The table lifter means the operation of the movable frameelevation motor 349 of the movable frame elevation mechanism 347. Theboard regulating cylinder means the operation of an air cylinder 355 dof the board regulation mechanism 355. The camera X-shaft means theoperation of the camera X-shaft movement motor 381. The camera X-shaftmark-1 movement means the operation of the camera X-shaft movement motor381 for movement to either one of the two positional alignment marks1005A and 1005B of the printed board 5 by means of the recognitioncamera 380. The camera X-shaft mark-2 movement means the operation ofthe camera X-shaft movement motor 381 for movement to the other one ofthe two positional alignment marks 1005A and 1005B of the printed board5 by means of the recognition camera 380. The printing head shaft meansthe operation of the motor for moving the squeegee, i.e., the operationof the printing head section horizontal movement motor 376 of theprinting head section horizontal movement mechanism 373. The screencorrection X-shaft means the operation of the screen table sectionhorizontal movement motor 363 of the screen table section horizontalmovement mechanism 361. The screen correction (rotation) θ-shaft meansthe operation of the 0table rotating, drive device 362 d of the screentable section rotation mechanism 362. The recognition means therecognition operation by the recognition camera 380. The mark-1recognition means the recognition operation of either one of the twopositional alignment marks 1005A and 1005B of the printed board 5 by therecognition camera 380. The mark-2 recognition means the recognitionoperation of the other one of the two positional alignment marks 1005Aand 1005B of the printed board 5 by the recognition camera 380.

That is, the control unit 399 controls the board loader 330 and theboard unloader 331 on the basis of a signal from the board detectionsensor 353 provided for the board stopper 352. By this operation, thecontrol unit 399 performs the loading of the board 311 onto the supportbase 340 by means of the board loader 330 and the unloading of the board311 from the support base 340 by means of the board unloader 311,roughly in synchronism in the board loading and unloading direction X1.

The control unit 399 also performs roughly in synchronism the support ofthe board 311 on the support base 340 in accordance with the elevatingoperation of the support base 340 by the support base elevationmechanism 342, the positioning of the board 311 on the support base 340by the board regulation mechanism 355, the upward movement of themovable frame 346 by the movable frame elevation mechanism 347, thehorizontal movement of the table section 320 in the direction of thearrow Y by the table section horizontal movement mechanism 322, and thepositioning of the board 311 in the recognition position by the upwardmovement of the movable frame 346 and the horizontal movement of thetable section 320.

Furthermore, the control unit 399 finds the amount of positionalcorrection for performing the relative positional alignment of the board311 with the screen 312 on the basis of the positions of the referenceposition marks of the board 311 and the screen 312 recognized by therecognition camera 380. Then, the control unit 399 controls the tablesection horizontal movement mechanism 322, the screen table sectionhorizontal movement mechanism 361, and the screen table section rotationmechanism 362 on the basis of the found amount of positional correctionto perform the relative positional alignment of the board 311 with thescreen 312.

In FIG. 61, the devices and the sensors connected to the control unit399 are as follows. In FIG. 61, reference numeral 300 denotes a monitortelevision for displaying various operations, results of recognition,results of printing, and so on, 301 denotes a printer for outputtingvarious data, 302 a main operation panel, 303 a sub-operation panel, and304SY an AC servo motor driver for controlling the AC servo motor thatis the table section horizontal movement motor 325 of the table sectionhorizontal movement mechanism 322. Reference numeral 304ST denotes an ACservo motor driver for controlling the AC servo motor that is themovable frame elevation motor 349 of the movable frame elevationmechanism 347. Reference numeral 304SST denotes an AC servo motor driverfor controlling the AC servo motor that is the support base elevationmotor 345.

Reference numeral 304CX denotes an AC servo motor driver for controllingthe AC servo motor that is the camera X-shaft movement motor 381.Reference numeral 304CY denotes an AC servo motor driver for controllingthe AC servo motor that is the camera Y-shaft movement motor 383.Reference numeral 304SQ denotes an AC servo motor driver for controllingthe AC servo motor that is the printing head section horizontal movementmotor 376. Reference numeral 304SX denotes an AC servo motor driver forcontrolling the AC servo motor that is the screen table sectionhorizontal movement motor 363. Reference numeral 304Sθ denotes an ACservo motor driver for controlling the AC servo motor that is theθ-table rotating drive device 362 d. The AC servo motor drivers areconnected to the control unit 399 and executes the driving control ofthe AC servo motors corresponding to the respective AC servo motordrivers via the respective AC servo motor drivers under the control ofthe control unit 399

The control unit 399 is further connected to a pair of drive motors 330d of the board loader 330, a pair of drive motors 331 d (a pair of drivemotors corresponding to the pair of drive motors 330 d of the boardloader 330) of the board unloader 331, a pair of drive motors 308 of theboard conveyance mechanism 351, an air cylinder 355 d of the boardregulation mechanism 355 via a solenoid valve 305 c for controlling theair cylinder 355 d, and a board stopper air cylinder 352 d of the boardstopper 352 via a solenoid valve 305 s for controlling the board stopperair cylinder 352 d.

The control unit 399 is further connected to the board detection sensor353, the board detection sensor 306in located on the entrance side ofthe board loader 330, the board detection sensor 306 out located on theexit side of the board loader 330, and the board detection sensor 307located on the entrance side of the board unloader 331. The informationdetected by the sensors are inputted to the control unit 399, and thedevices connected to the control unit 399 are appropriately driven to becontrolled under the control of the control unit 399.

The operation of the sixth embodiment will be described next.

In the screen printing apparatus 310, the control unit 399 controls theboard loader 330 and the board unloader 331 on the basis of the signalfrom the board detection sensor 353 in a state in which the movableframe 346 is positioned in the lowered position by the movable frameelevation mechanism 347. By this operation, the unloading of thealready-printed board 311 on the support base 340 and the loading of thepre-printing board 311 onto the support base 340 are performed.

That is, the board unloader 331 unloads the already-printed board 311 onthe support base 340 in the board loading and unloading direction X1.When the board detection sensor 353 comes to detect no board 311, theboard loader 330 loads the pre-printing board 311 onto the support base340 in the board loading and unloading direction X1.

Next, the control unit 399 operates the support base elevation mechanism342, the board regulation mechanism 355; the movable frame elevationmechanism 347, and the table section horizontal movement mechanism 322roughly in synchronism. By this operation, the pre-printing board 311 onthe support base 340 is moved to the recognition position in a shorttime and then positioned.

That is, by moving up the support base 340 to which the pre-printingboard 311 has been loaded with respect to the movable frame 346 by thesupport base elevation mechanism 342, the board 311 is supported to thesupport pins 340 a of the support base 340, and the board regulationmechanism 355 positions the board 311 on the support base 340.

Furthermore, roughly in synchronization with the above operations, themovable frame elevation mechanism 347 moves up the movable frame 346 tothe raised position, and the table section horizontal movement mechanism322 moves the table section 320 so as to make the table sectionhorizontally advance and retreat in the direction of the arrow Y. Bythis operation, the board 311 on the support base 340 is moved to therecognition position in a short time.

In the state in which the board 311 is located in the recognitionposition, the control unit 399 moves the recognition camera 380 so as tomake the camera horizontally advance and retreat in the direction of thearrow X, and the table section 320 is moved so as to horizontallyadvance and retreat in the direction of the arrow Y by the table sectionhorizontal movement mechanism 322. By this operation, the recognitioncamera 380 recognizes the reference position mark of the board 311 (whenthere is a plurality of reference position marks, the recognition camera380 and the table section 320 are respectively moved to recognize therespective reference position marks). The position of the recognizedreference position mark is inputted as an electric signal from therecognition camera 380 to the control unit 399.

The control unit 399 moves the recognition camera 380 so as to make thecamera horizontally advance and retreat in the direction of the arrow Xand in the direction of the arrow Y, thereby making the recognitioncamera 380 recognize the reference position mark of the screen 312 (whenthere is a plurality of reference position marks, the recognition camera380 is moved to recognize the respective reference position marks). Theposition of the recognized reference position mark is inputted as anelectric signal from the recognition camera 380 to the control unit 399.

Then, the control unit 399 controls the table section horizontalmovement mechanism 322, the screen table section horizontal movementmechanism 361, and the screen table section rotation mechanism 362roughly in synchronism on the basis of the position of the referenceposition marks of the board 311 and the screen 312 recognized by therecognition camera 380, performing the relative positional alignment ofthe board 311 with the screen 312 in a short time.

That is, the table section horizontal movement mechanism 322 makes thetable section 320 horizontally advance and retreat in the direction ofthe arrow Y. Moreover, the screen table section 360 that supports thescreen 312 is moved by the screen table section horizontal movementmechanism 361 in the direction of the arrow X and forwardly andreversely rotated within the horizontal plane roughly parallel to theboard 311 on the support base 340 by the screen table horizontal rotarymechanism 362. By this operation, the board 311 and the screen 312 arepositioned relative to each other in a short time.

In this state, the control unit 399 prints the printing paste on theboard 311 via the screen 312 by squeegeeing the printing paste by meansof the printing squeegee 372 of the printing head section 370.

After the end of the printing, the control unit 399 moves the movableframe .346 down to the lowered position by means of the movable frameelevation mechanism 347 and controls again the board loader 330 and theboard unloader 331 on the basis of the signal from the board detectionsensor 353. By this operation, the already-printed board 311 on thesupport base 340 is unloaded in the board loading and unloadingdirection X1, and the pre-printing board 311 is loaded onto the supportbase 340 in the board loading and unloading direction X1.

Subsequently, the operations similar to those described above arerepeated to successively perform the printing of the board 311.

FIG. 48 is a flowchart showing the processes of the screen printingmethod.

The screen printing method by the screen printing apparatus 310 will besequentially described below with reference to FIG. 48 step by step.

First of all, in a board loading and unloading process (step S41), thepre-printing board 311 is loaded onto the support base 340 in the boardloading and unloading direction X1 by the board loader 330, and thealready-printed board 311 on the support base 340 is unloaded in theboard loading and unloading direction X1 by the board unloader 331immediately before the loading of the pre-printing board 311 by theboard loader 330.

Next, in a board positioning process (step S42), the support base 340onto which the pre-printing board 311 has been loaded is moved up withrespect to the movable frame 346 by the support base elevation mechanism342 to support the board 311 on the support base 340, and the board 311is positioned on the support base 340 by the board regulation mechanism355. Furthermore, roughly in synchronization with these operations, themovable frame 346 is moved up by the movable frame elevation mechanism347, and the table section 320 is made to horizontally advance andretreat in the direction of the arrow Y by the table section horizontalmovement mechanism 322. By this operation, the board 311 on the supportbase 340 is positioned in a short time in the specified recognitionposition where the reference position mark recognition is performed bythe recognition camera 380.

In a board reference position mark recognition process (step S43), inaccordance with the horizontal movement of the recognition camera 380 inthe direction of the arrow X and the horizontal movement of the tablesection 320 in the direction of the arrow Y by the table sectionhorizontal movement mechanism 322, the reference position mark (refer to1005A and 1005B) of the board 311 located in the recognition position isrecognized by the recognition camera 380 (when there is a plurality ofreference position marks, the recognition camera 380 and the tablesection 320 are each moved to make the recognition camera 380 recognizethe respective reference position marks).

In a screen reference position mark recognition process (step S45), inaccordance with the horizontal movement of the recognition camera 380 inthe direction of the arrow X and in the direction of the arrow Y, therecognition camera 380 is made to recognize the reference position markof the screen 312 (refer to 1003A and 1003B of the screen 3 in FIG. 32and FIG. 33) (when there is a plurality of reference position marks, therecognition camera 380 and the table section 320 are each moved to makethe recognition camera 380 recognize the respective reference positionmarks).

As shown in step S44, this screen reference position mark recognitionprocess is not normally required to be executed every producingoperation but required to be executed only in the first process if thescreen is not detached. However, when there is a margin in the producingoperation of the whole line, the process may be executed every time inorder to secure the reliability of the every producing operation.

In the positional correction process (step S46), the table sectionhorizontal movement mechanism 322, the screen table section horizontalmovement mechanism 361 and the screen table section rotation mechanism362 are controlled by the control unit 399 on the basis of the positionof each reference position mark recognized by the recognition camera380, by which the relative positional alignment of the board 311 withthe screen 312 is performed in a short time.

That is, the table section 320 is made to horizontally advance andretreat in the direction of the arrow Y by the table section horizontalmovement mechanism 322. Moreover, the screen table section 360 thatsupports the screen 312 is moved in the direction of the arrow X by thescreen table section horizontal movement mechanism 361 and rotatedforwardly and reversely within a horizontal plane roughly parallel tothe board 311 on the support base 340 by the screen table horizontalrotary mechanism 362. By this operation, the relative positionalalignment of the board 311 with the screen 312 is performed in a shorttime.

In the printing process (step S47), the printing paste is printed on theboard 311 via the screen 312 by squeegeeing the printing paste by theprinting squeegee 372 of the printing head section 370.

After the end of the printing, the program flow returns again to theboard loading and unloading process, and similar processes willsubsequently be repeated.

According to the sixth embodiment described above, the control unit 399controls the board loader 330 and the board unloader 331 on the basis ofthe signal from the board detection sensor 353 and performs the loadingof the board 311 onto the support base 340 by the board loader 330 andthe unloading of the board 311 from the support base 340 by the boardunloader 331 in the board loading and unloading direction X1 roughly insynchronism.

Moreover, the control unit 399 performs roughly in synchronism thesupport of the board 311 on the support base 340 in accordance with theelevating operation of the support base 340 by the support baseelevation mechanism is 342, the positioning of the board 311 on thesupport base 340 by the board regulation mechanism 355, the upwardmovement of the movable frame 346 of the support base elevationmechanism 342 by the movable frame elevation mechanism 347, thehorizontal movement of the table section 320 in the direction of thearrow Y by the table section horizontal movement mechanism 322, and thepositioning of the board 311 in the recognition position where thereference position mark recognition is performed by the recognitioncamera 380 by the upward movement of the movable frame 346 of thesupport base elevation mechanism 342 and the horizontal movement of thetable section 320.

Furthermore, the control unit 399 controls roughly in synchronism thetable section horizontal movement mechanism 322, the screen tablesection horizontal movement mechanism 361, and the screen table sectionrotation mechanism 362 on the basis of the positions of the referenceposition marks of the board 311 and the screen 312 recognized by therecognition camera 380, thereby performing the relative positionalalignment of the board 311 with the screen 312.

Therefore, the times required for the replacement of the board 311 andthe recognition of the reference position mark by the recognition camera380 can be remarkably reduced. By this operation, the printing time canbe remarkably reduced.

Moreover, the ball thread shaft 343 and the guide shafts 327 of the ballthread mechanism are commonly used by the support base elevationmechanism 342 and the movable frame elevation mechanism 347.

That is, the ball thread shaft 343 generates a screwing action betweenthe shaft and the ball thread nut 344 of the support base elevationmechanism 342 by being forwardly and reversely rotated in accordancewith the operation of the support base elevation motor 345, therebymoving up and down the support base 340 along the guide shafts 327 viathe support base elevation guides 341 with respect to the movable frame346.

Moreover, the ball thread shaft 343 generates a screwing action betweenthe shaft and the ball thread nut 348 with respect to the table section320 by the forward and reverse rotation of the ball thread nut 348 ofthe movable frame elevation mechanism 347 in accordance with theoperation of the movable frame elevation motor 349, thereby moving upand down the movable frame 346 together with the guide shaft 327.

Therefore, the weight of the portion to be moved up and down can bereduced, and it is impossible to cause the increase in the inertia as aconsequence of the increase in weight dissimilar to the prior art screenprinting apparatus 3110 described in Unexamined Japanese PatentPublication No. 7-329276 shown in FIG. 42 and FIG. 51, and there iscaused no such issue that the hunting in accordance with the verticalmovement of the support base 340 and the movable frame 346 appearssignificantly. With this arrangement, there is no need for waitinguntil, for example, the hunting disappears, and the time required forthe completion of the printing can be remarkably reduced. Moreover, thetravel speed can be increased by the reduction in weight of theelevation device.

Furthermore, a board stopper 352 is provided on the support base 340 soas to be able to advance and retreat, and the board stopper 352 stopsthe board 311 at the specified board support position on the supportbase 340 by being engaged with the fore end portion of the pre-printingboard 311 to be loaded onto the support base 340 by the board loader330. Furthermore, the board detection sensor 353 for detecting thepresence or absence of the board 311 on the support base 340 is providedfor the board stopper 352. The control unit 399 controls the boardloader 330 and the board unloader 331 on the basis of the boarddetection signal from the board detection sensor 353.

Therefore, it is enabled to reliably prevent the contact between theloaded pre-printing board 311 and the already-printed board 311 to beunloaded when replacing the board 311 and to roughly synchronize theloading with the unloading of the board 311.

According to the present invention as described above, the board isloaded onto the support base in the specified board loading andunloading direction by the board loading device, and the board on thesupport base is unloaded in the board loading and unloading direction bythe board unloading device roughly in synchronization with the loadingof the board by the board loading device.

Then, by moving up the support base onto which the board has been loadedwith respect to the movable frame by the support base elevation device,the board is supported on the support base and positioned on the supportbase by the board regulation device. Further, in synchronization withthese operations, by moving up the movable frame by the movable frameelevation device with respect to the table section and making the tablesection horizontally advance and retreat in the direction roughlyperpendicular to the board loading and unloading direction by the tablesection horizontal movement device, the board on the support base ispositioned in the specified position.

Then, in accordance with the horizontal movement of the recognitioncamera in the board loading and unloading direction and the horizontalmovement of the table section in the direction roughly perpendicular tothe board loading and unloading direction by the table sectionhorizontal movement device, the reference position mark preparatorilygiven to the board is recognized by the recognition camera.

Then, in accordance with the horizontal movement of the recognitioncamera in the board loading and unloading direction and in the directionroughly perpendicular to the board loading and unloading direction, thereference position mark preparatorily given to the screen is recognizedby the recognition camera.

The relative positional alignment of the board with the screen isperformed on the basis of the position of each reference position markrecognized by the recognition camera by making the table sectionhorizontally advance and retreat in the direction roughly perpendicularto the board loading and unloading direction by means of the tablesection horizontal movement device, moving the screen table section thatsupports the screen in the board loading and unloading direction bymeans of the screen table section horizontal movement device, andforwardly and reversely rotating the screen table section in thehorizontal plane roughly parallel to the board on the support base bymeans of the screen table section rotation device.

Then, the printing paste is printed on the board via the screensupported by the screen table section by means of the printing headsection 370 arranged above the screen table section.

Therefore, the times required for the replacement of the board and therecognition of the reference position mark by means of the recognitioncamera can be reduced. With this arrangement, the printing time can bereduced.

According to the present invention, the control means performs theloading of the board onto the support base by the board loading deviceand the unloading of the board from the support base by the boardunloading device roughly in synchronism in the specified board loadingand unloading direction.

Moreover, the control means performs roughly in synchronism the supportof the board on the support base in accordance with the elevatingoperation of the support base by the support base elevation device, thepositioning of the board on the support base by the board regulationdevice, the vertical movement of the movable frame by the movable frameelevation device, the horizontal movement of the table section roughlyperpendicular to the board loading and unloading direction by the tablesection horizontal movement device, and the positioning of the board inthe specified position where the reference position mark recognition isperformed by the recognition camera in accordance with the verticalmovement of the movable frame and the horizontal movement of the tablesection.

Furthermore, the control means controls the table section horizontalmovement device, the screen table section horizontal movement device,and the screen table section rotation device on the basis of thepositions of the reference position marks of the board and the screenrecognized by the recognition camera, thereby performing the relativepositional alignment of the board with the screen.

Therefore, the times required for the replacement of the board and therecognition of the reference position mark by the recognition camera canbe reduced. By this operation, the printing time can be reduced.

The support base is supported by the guide shafts fixed to the movableframe so as to be able to move up and down. The support base elevationdevice is provided with: the ball thread mechanism constructed of theball thread shaft having the peripheral surface on which the ball threadis formed and the ball thread nut that is provided on the support baseand meshed with the ball thread shaft; and the support base elevationmotor for forwardly and reversely rotating the ball thread shaft of theball thread mechanism, the mechanism and the motor being provided on themovable frame. Furthermore, the movable frame elevation device isprovided with: the ball thread mechanism constructed of the ball threadshaft commonly used for the support base elevation device and the ballthread nut that is meshed with the ball thread shaft and rotatablysupported by the table section; and the movable frame elevation motorfor forwardly and reversely rotating the ball thread nut of the ballthread mechanism, the mechanism and the motor being provided on thetable section. The ball thread shaft and the guide shafts of the ballthread mechanism are commonly used by the support base elevation deviceand the movable frame elevation device.

Therefore, the weight of the portion to be moved up and down can bereduced, and the hunting in accordance with the vertical movement of thesupport base and the movable frame can be restricted to the minimum.With this arrangement, there is no need for waiting until, for example,the hunting disappears, and the time required for the completion of theprinting can be remarkably reduced.

Moreover, the board stopper is provided on the support base so as to beable to advance and retreat, and the board stopper stops the board inthe specified position on the support base by being engaged with thefore end portion of the board 311 to be loaded onto the support base bythe board loading device. Furthermore, the board detection sensor fordetecting the presence or absence of the board on the support base isprovided for the board stopper. The control means controls the boardloading device and the board unloading device on the basis of the boarddetection signal from the board detection sensor.

Therefore, it is enabled to reduce the times required for thereplacement of the board and the recognition of the reference positionmark by the recognition camera and reliably prevent the contact betweenthe loading board and the board 311 to be unloaded when replacing theboard. With this arrangement, the printing time can be reduced.

Moreover, the cushioning member may be provided on the surface thatbelongs to the board stopper and is engaged with the board. With thisarrangement, the inertial force of the loading board can be attenuated,and the vibration of the board can be stopped in an extremely shorttime.

According to the screen printing method of the present invention, theboard is first loaded in the specified board loading and unloadingdirection by the board loading device onto the support base upward anddownward movably supported by the movable frame that can move up anddown with respect to the table section in the board loading andunloading operation. Moreover, roughly in synchronization with theloading of the board by the board loading device, the board on thesupport base is unloaded in the board loading and unloading direction bythe board unloading device.

Next, in the board positioning operation, the board is supported on thesupport base by moving up the support base onto which the board has beenloaded by the support base elevation device with respect to the movableframe and positioned on the support base by the board regulation device.Furthermore, roughly in synchronization with these operation, themovable frame is moved up with respect to the table section by themovable frame elevation device, and the table section is made tohorizontally advance and retreat in the direction roughly perpendicularto the board loading and unloading direction by the table sectionhorizontal movement device. By this operation, the board on the supportbase is positioned in the specified position.

In the board reference position mark recognition operation, thereference position mark preparatorily given to the board is recognizedby the recognition camera in accordance with the horizontal movement ofthe recognition camera in the board loading and unloading direction andthe horizontal movement of the table section in the direction roughlyperpendicular to the board loading and unloading direction by the tablesection horizontal movement device.

In the screen reference position mark recognition operation, thereference position mark preparatorily given to the screen is recognizedby the recognition camera in accordance with the horizontal movement ofthe recognition camera in the board loading and unloading direction andin the direction roughly perpendicular to the board loading andunloading direction. This screen reference position mark recognitionoperation is not always required to be performed every printing pasteprinting operation on the board and is allowed to be performed beforethe printing paste printing operation on the specified number of boards.

In the positional correction operation, the table section is moved tohorizontally advance and retreat in the direction roughly perpendicularto the board loading and unloading direction by the table sectionhorizontal movement device on the basis of the position of eachreference position mark recognized by the recognition camera. Moreover,the screen table section that supports the screen is moved in the boardloading and unloading direction by the screen table horizontal movementdevice and forwardly and reversely rotated in the horizontal planeroughly parallel to the board on the support base by the screen tablesection rotation device. By this operation, the relative positionalalignment of the board with the screen is performed.

In the printing operation, the printing paste is printed on the boardvia the screen supported by the screen table section by the printinghead section arranged above the screen table section.

In the screen printing apparatus of the present invention, the controlmeans performs roughly in synchronism the loading of the board onto thesupport base by the board loading device and the unloading of the boardfrom the support base by the board unloading device in the specifiedboard loading and unloading direction.

Moreover, the control means performs roughly in synchronism the supportof the board on the support base in accordance with the elevatingoperation of the support base by the support base elevation device, thepositioning of the board on the support base by the board regulationdevice, the upward movement of the movable frame by the movable frameelevation device, the horizontal movement of the table section in thedirection roughly perpendicular to the board loading and unloadingdirection by the table section horizontal movement device, and thepositioning of the board in the specified position where the referenceposition mark recognition is performed by the recognition camera by theupward movement of the movable frame and the horizontal movement of thetable section.

Furthermore, the control means controls roughly in synchronism the tablesection horizontal movement device, the screen table section horizontalmovement device, and the screen table section rotation device on thebasis of the positions of the respective reference position marks of theboard and the screen recognized by the recognition camera, therebyperforming the relative positional alignment of the board with thescreen.

In the screen printing apparatus of the present invention, the supportbase elevation device generates a screwing action between the ballthread shaft and the ball thread nut that belongs to the ball threadmechanism and is meshed with the ball thread shaft by forwardly andreversely rotating the ball thread shaft of the ball thread mechanism bymeans of the support base elevation motor. By this operation, thesupport base elevation device moves up and down the support base alongthe guide shafts fixed to the movable frame with respect to the movableframe.

Moreover, the movable frame elevation device generates a screwing actionbetween the ball thread nut and the ball thread shaft commonly used forthe support base elevation device by forwardly and reversely rotatingthe ball thread nut of the ball thread mechanism rotatably supported bythe table section by means of the movable frame elevation motor. By thisoperation, the movable frame is moved up and down by the movable frameelevation device with respect to the table section.

In other words, the ball thread shaft of the ball thread mechanismgenerates a screwing action between the shaft and the ball thread nut ofthe ball thread mechanism by being forwardly and reversely rotated bythe support base elevation motor of the support base elevation device,thereby moving up and down the support base along the guide shafts withrespect to the movable frame.

Moreover, the ball thread shaft of the ball thread mechanism generates ascrewing action between the shaft and the ball thread nut by the forwardand reverse rotation of the ball thread nut of the ball thread mechanismby the movable frame elevation motor of the movable frame elevationdevice, by which the shaft is moved up and down with respect to thetable section, and the movable frame is moved up and down together withthe guide shaft.

In the screen printing apparatus of the present invention, the boardstopper provided on the support base so as to be able to advance andretreat stops the board in the specified position on the support base bybeing engaged with the fore end portion of the loading board onto thesupport base by the board loading device. The board detection sensorprovided for the board stopper detects the presence or absence of aboard on the support base. The control means controls the board loadingdevice and the board unloading device on the basis of the boarddetection signal from the board detection sensor.

In the screen printing apparatus of the present invention, the boardstopper provided on the support base so as to be able to advance andretreat stops the board in the specified position on the support base bybeing engaged with the fore end portion of the board loading onto thesupport base by the board loading device. In this stage, the boardstopper is engaged with the fore end portion of the board via thecushioning member provided on the surface of engagement with the board.

(Seventh Embodiment)

The seventh embodiment of the present invention is related to a printingscreen cleaning method and device and a wiping member backup member,subjected to, for example, temporarily mounting and mounting of anelectronic component by printing a printing paste such as a solderpaste, an insulating paste, or the like on a circuit board provided witha wiring pattern, and utilized for the manufacturing of an electroniccircuit board or in a similar case.

Before explaining the seventh embodiment, a conventional issue will bedescribed first.

The screen printing is suitable for the printing of a solder paste or aninsulating paste on a circuit board in manufacturing an electroniccircuit board as described above. With the increasing wiring density andcomponent mounting density of electronic circuit boards, the printingpaste printing pattern is also made fine. This causes the defectivemounting and defective insulation of components even with a slightshortage of the amount of printing and becomes a reason for theshort-circuit and excessive insulation between wiring patterns even witha slight surplus in the amount of printing and a slight displacement ofthe printing position. Therefore, high-accuracy printing is required.

However, the printing paste supply holes formed in a specified patternthrough a printing screen are also made fine in accordance with theprinting pattern, and the mask separation of the printing paste isgetting worse and worse. As shown in FIG. 73A and FIG. 73B, the printingpaste tends to remain stuck to the inside of the printing paste supplyholes 610 of a printing screen 601 and lodge in the end portions of anelongated pattern and so on. Depending on cases, the printing pastesometimes lodges in the entire printing paste supply hole. As describedabove, the printing paste 612 that stays and lodges in the printingpaste supply hole 610 turns around and adheres to is the lower surfaceof the printing screen 601. The printing paste 612 oozes out of thespecified printing pattern in the next printing stage or becomes printedon a portion other than the specified pattern, for which theaforementioned issue cannot completely be solved.

Accordingly, the present applicant has already proposed a cleaningdevice as shown in FIG. 72, which is provided with a cleaning head 602for cleaning the printing screen 601 from the lower surface after thescreen is used for printing. The cleaning head 602 is provided with asheet-shaped wiping member 605 that is unwound from a supply section 603and wound around a winding section 604, and a backup member 606 thatbacks up this wiping material 605 partway from under and presses themember against the printing screen 601, putting the member in slidingcontact with the printing screen 601 with the movement of the cleaninghead 602. On the backup surface of the backup member 606 is provided asuction port(s) 609 in a suction region 608 perpendicular to the slidingdirection.

With this arrangement, the cleaning head 602 can improve the effect ofcleaning the printing screen 601 by sucking the lodging printing paste612 to the wiping member 605 side to make the paste adhere to the memberby the suction via the wiping member 605 through the suction port 609 asshown in FIG. 73C in addition to the wiping by sliding the wiping member605 on the printing screen 601. This arrangement is effective foreliminating the issues described above.

Although the present inventor and others have put the above-mentionedpreviously proposed technology into practical use, there is still aconcern about the elimination of the defective printing as describedhereinabove. The present inventors are carrying out further examinationinto the above-mentioned matter and attempting to improve the same.According to the aforementioned previous proposal, as shown in FIG. 73C,even when the suction region 608 of the backup member 606 passes underthe printing paste supply hole 610 of the printing screen 601 to suckthe printing paste 612 that has stayed and lodged in the printing pastesupply hole 610, make the paste once adhere to the wiping member 605side, and accommodate and keep the paste in a pocket portion 613 drawnin to the suction port 609, the printing paste 612 that has been onceaccommodated and kept in the pocket portion 613 is left in spots inportions on the lower surface of the printing screen 601 along which thebackup member 606 and the wiping member 605 are passing as shown in FIG.73E after the establishment of a positional relation such that thesliding portion of the wiping member 605 passes through the printingpaste supply hole 610 and then faces the surface of the printing screen601 by the operation of the backup member 606 as shown in FIG. 73D.

It is estimated that the printing paste 612 has a much smaller adhesionpower to the printing screen 601 made of a metal than its adhesion powerto the wiping member 605 made of paper or the like and the printingpaste 612 once stuck to and kept by the wiping member 605 is to becarried away while being slid relative to the printing screen 601 side.However, a friction between the printing paste 612 and the printingscreen 601 is not zero. Consequently, the printing paste 612 graduallyshifts backward between the printing screen 601 and the wiping member605 due to the friction between the paste and the printing screen 601when the printing paste 612 slides between the wiping member 605 and theprinting screen 601, and sometimes eventually falls off the wipingmember 605 and remains stuck to the lower surface of the printing screen601, causing an issue.

Moreover, even by the aforementioned suction, the paste sometimes staysinside the printing paste supply holes 610 of the printing screen 601.This is presumably attributed to the fact that the pocket portion 613formed by a pull into the suction port 609 by the wiping member 605leaves a part of the printing paste 612 that has stayed or lodged in theprinting paste supply hole 610 in the printing paste supply hole 610 dueto the fact that the amount of the lodging paste exceeds theaccommodation capacity of the pocket portion 613.

The object of the seventh embodiment of the present invention is toprovide a printing screen cleaning method and device and a wiping memberbackup member, capable of sufficiently stably removing the printingpaste that is stuck to the lower surface of the printing screen andstays in the printing paste supply holes and achieving high-qualitysolder paste printing with high productivity.

The printing screen cleaning method and device and the wiping memberbackup member of the seventh embodiment of the present invention will bedescribed in detail below with the embodiments thereof referring to FIG.62A through FIG. 66, for the perception of the present invention.

As shown in FIGS. 62A through FIG. 62D, FIG. 63A, FIG. 63B, FIG. 64, andFIG. 66, the seventh embodiment is one example in which, by sliding acleaning web 505 that is a wiping member made of paper on the lowersurface of a printing screen 504 for supplying a solder paste 503 thatserves as a printing paste for the mounting of an electroniccomponention a circuit board 502 as one example of an object to beprinted that serves as a circuit-forming body through a hole 501 thatserves as a printing paste supply section of a specified pattern whilebacking up the web by a backup member 506 so as to suck the printingpaste 503 stuck to the lower surface via the wiping member through asuction port 508 provided in a suction region 507 for suction in adirection roughly perpendicular to the sliding direction while wipingthe solder paste 503 off the lower surface, the solder paste 503 isstuck to the lower surface of the printing screen 504, and the solderpaste 503 that lodges in the hole 501 is sucked to the cleaning web 505side so as to be stuck to and kept by the web for the cleaning of theprinting screen 504; and the example is applied to a screen printingapparatus as shown in FIG. 66.

In this screen printing apparatus, a circuit board 502 placed on aprinting stage 531 is positioned and held in a specified position on ahorizontal plane by a positioning mechanism 530, and thereafter, theprinting stage 531 is moved up to a specified position by an elevationdevice 532 that utilizes an air cylinder or the like, by which thecircuit board 502 is lifted up to the printing position of the printingscreen 504 and subjected to screen printing. Above the screen 504, oneor a plurality of squeegees 533 and 534 of varied sizes and differentmaterials is supported so as to be able to be moved up and down by aircylinders 535 and 536. After the squeegee to be used is moved down andpressurized on the printing screen 504, the squeegee 533 or the squeegee534 is moved in the direction in which it is inclined on the printingscreen 504 by the rotative driving of a threaded shaft 537 of which theforward and reverse rotation is selected. The squeegee is made toadvance while pressurizing the printing paste 503 supplied onto thescreen 504 against the upper surface of the screen 504, therebysupplying the paste according to the shape of the pattern of the holes501 on the circuit board 502 through the holes 501 provided in portionsof the printing screen 504. Subsequently, the screen 504 is separatedfrom the circuit board 502 by the upward movement of the printing screen504 or the downward movement of the circuit board 502 or both of them,leaving the solder paste 503 supplied onto the circuit board 502, forthe achievement of the printing.

Even if the solder paste 503 stays by adhering to the lower surface ofthe screen 504 or lodging in the end portion in the lengthwise directionof the hole 501 as shown in FIG. 62A after the screen printing asdescribed above, by wiping the paste by sliding the cleaning web 505 inthe direction indicated by the arrow in FIG. 62B or in the directionopposite to the direction on the lower surface of the screen 504 withthe cleaning web 505 backed up by the backup member 506 according to theaforementioned cleaning, and sucking the paste via the cleaning web 505through the suction port 508 provided in the suction region 507 extendedin the direction roughly perpendicular to the sliding direction, thesolder paste 503 that is stuck to the lower surface of the screen 504 orstays in the hole 501 is sucked to the cleaning web 505 side so as to bestuck to and kept by the web. Therefore, more effective cleaning than inthe case of only the wiping can be achieved, and the accuracy ofprinting of the solder paste 503 on the circuit board 502 is increasedby that much.

However, the present invention is not limited to the one that has beendescribed hereinabove and shown in the drawings and is effective when itis applied to a variety of screen printing apparatuses such that theprinting is performed by supplying various sorts of printing pastesincluding, for example, an insulating paste intended for providinginsulation of the circuit board 502 from electronic components to bemounted on the board other than the solder paste 503 on various sorts ofobjects to be printed through the printing paste supply section formedin accordance with the specified pattern of the screen 504, and theprinting paste such as the solder paste 503 is left on the lower surfaceof the screen 504 and the like even by the aforementioned cleaning,exerting bad influence on the next printing. Moreover, the printingpaste supply section is only required to be able to supply the printingpaste onto the object to be printed according to the specified pattern,and various types such as a mesh section other than the hole 501 can beadopted so long as the printing paste is allowed to pass through itaccording to the specified pattern. The wiping member is only requiredto be made of a material that brings a wiping function into effect onthe screen 504 with at least one of the adhesive property and thecatching property of the printing paste made higher than that of thelower surface of the screen 504 or for a similar reason and has an airpermeability such that the suction from the back surface takes effect onthe surface side. Various sorts of sheet materials of unwoven cloth,cloth, and knitting can be used besides paper. The backup member 506,which is made of a metal in terms of durability and processability, isbasically only required to bring a backup function into effect, and anonmetal material of synthetic resin or the like can also be adopted.

In addition to the aforementioned effective cleaning, the cleaningmethod of the seventh embodiment has a further particular operationthat, when a backup release section 505 a where the backup is partiallyreleased by a groove 509 arranged parallel to the suction region 507 ofthe backup member 506 of the cleaning web 505 faces the solder paste 503stuck to the lower surface of the screen 504 as shown in FIG. 62B, aportion that belongs to the cleaning web 505 and is supported by anopening edge 509 a on the rear side in the sliding direction of thegroove 509 in the backup release section 505 a operates as a scrapingedge 505 b of the solder paste 503 so as to scrape the solder paste 503stuck to the lower surface of the screen 504, and the backup releasesection 505 a retreats into the groove 509 to form a pocket 511 foraccommodating and keeping the scraped solder paste 503. Therefore, theamount of solder paste 503 removed and carried away from the screen 504by the cleaning web 505 is increased to allow the cleaning effect to befurther improved.

Here, in the state in which the cleaning by the backup release section505 a precedes the cleaning by the suction region 507 shown in FIG. 62Band FIG. 62C, there is produced the synergetic effect that the amount ofsolder paste 503 to be accommodated in the pocket 511 formed by pullingthe cleaning web 505 into the suction port 508 through the cleaning inthe suction region 507 is reduced by the amount of solder paste 503removed through the cleaning by the backup release section 505 a, andthe amount of solder paste 503 that is staying and lodging in the hole501 and is able to be sucked and accommodated is increased, for theimprovement of the cleaning effect.

In the state in which the cleaning by the backup release section 505 asucceeds the cleaning by the suction region 507 shown in FIG. 62D, thereis produced the synergetic effect that the cleaning by suction isassisted by scraping and removing the solder paste 503, which isaccommodated and kept in the pocket 511 formed by pulling the cleaningweb 505 into the suction port 508 in the cleaning portion by thepreceding suction region 507 and left behind on the lower surface of thescreen 504 as shown in FIG. 62D, through the cleaning by the backuprelease section 505 a as shown in FIG. 62D, for the improvement of thecleaning effect.

Although it is effective to achieve either one of these two cleaningstates, the cleaning effect is doubled by concurrently using both thecleaning manners. Moreover, it is enabled to cope with them by providingthe cleaning portion of the suction region 507 and the cleaning portionof the backup release section 505 a by the required number in repetitionin the sliding direction or providing a plurality of same cleaningportions arranged in accordance with the need. If two types of cleaningportions are arranged symmetrically about the center in the slidingdirection, then the same cleaning effect can be obtained by the slidingin either one of the forward and reverse directions, and thisarrangement is advantageous when performing cleaning by reciprocalsliding.

In order to achieve the cleaning method as described above, a cleaningdevice as shown in FIG. 66 is provided with a cleaning head 521, inwhich suction is performed via the cleaning web 505 through the suctionport 508 provided in the suction region 507 in the direction roughlyperpendicular to the sliding direction of a backup surface 506 a forperforming the backup while sliding the cleaning web 505 on the lowersurface of the screen 504 with the web backed up by the backup member506, and the cleaning head 521 is used with various sorts of backupmembers 506 shown in FIG. 63A through FIG. 65B selectively mounted.

The selected backup member 506 is supported so as to be able to move upand down by being mounted on the tip of an upwardly directed piston rod523 a of an air cylinder 523 that is one example of an elevation device522 on the cleaning head 521, so that the backup member 506 is able tobe pressurized against the screen 504 on the cleaning head 521 orrelease the pressurization. The cleaning head 521 is moved into or outof a position under the screen 504 from the standby position locatedbeside the screen 504 and reciprocally moved under the screen 504 by amovement device 524. The movement device 524 is constructed of a drivinggear 526 driven by being directly connected to a motor 525 arranged onthe cleaning head 521 and a rack 527 to be meshed with this driving gear526, as an example. By moving forwardly the cleaning head 521 to thescreen 504 side or reversely to the standby position side by rotativelydriving the driving gear 526 by selection between forward and reverserotations. Depending on the timing of forward and reverse rotations, thecleaning head 521 can also be reciprocally moved by the required numberof times under the screen 504.

The cleaning head 521 does not impede the printing operation of thesolder paste 503 on the circuit board 502 by the screen 504 in thescreen printing apparatus by standing by in the standby position duringthe printing operation. Every time the printing is performed once orevery time the printing is performed a specified number of times or oneach required occasion, the cleaning head 521 is moved under the screen504 by moving up the backup member 506, the aforementioned operation ofrepetitively performing the cleaning and getting ready for the nextprinting is executed, guaranteeing the stable performance ofhigh-accuracy printing for a long term.

The cleaning web 505 is extended between a supply section 541 and awinding section 542 along the backup surface 506 a of the backup member506, copes with the upward movement of the backup member 506 by the feedthereof from the supply section 541, and updates the cleaning regionsubjected to the cleaning while being backed up by the backup surface506 a by the feed from the supply section 541 and the winding in thewinding section 542. This updating is preferably performed in a state inwhich the cleaning web 505 is separated from the screen 504 in terms ofpreventing the solder paste 503 that has been wiped to the cleaning web505 side from being retransferred to the screen 504 side. For thispurpose, it is proper to move down the backup member 506 for the releaseof the pressurization of the cleaning web 505 against the screen 504 ormove the head into a position located out of the screen 504. It is to benoted that the slackening of the cleaning web 505 when thepressurization of the cleaning web 505 against the screen 504 isreleased by moving down the backup member 506 can be eliminated by thewinding in the winding section 542. Moreover, the state in which thepressurization of the cleaning web 505 against the screen 504 isreleased means that the cleaning head 521 is able to move under thescreen 504 without the cleaning operation and able to freely move byavoiding contact with the screen 504.

Every time the cleaning ends once, by winding the cleaning web 505 bythe winding section 542 in accordance with the feed and supply of thecleaning web 505 from the supply section 541, the cleaning can beperformed every time by the new cleaning web 505, and the aforementionedmore effective cleaning function can stably be maintained.

The suction ports 508 are provided in an array in a directionperpendicular to the sliding direction in the suction region 507 asshown in FIG. 63A and FIG. 65A. With this arrangement, the suction forceis increased by reducing the individual suction ports 508 while securingthe required amount of suction air depending on the total opening area,by which the suction efficiency is increased, guaranteeing theaforementioned cleaning function.

Furthermore, the suction ports 508 are formed in a slit-like forminclined in the sliding direction and formed so that the suction ports508 overlap in the direction perpendicular to the sliding direction.With this arrangement, the suction via the cleaning web 505 is Sconsistently effected on the screen 504 through any one of the suctionports 508 and is able to be continuously effected on the entire regionof the lower surface of the screen 564 by the successive continuouschange of the suction position.

In this case, the total aperture area of the suction ports 508 formed inan array is formed so that a value obtained by multiplying a flow rate Qof air that passes through the suction ports 508 by a velocity V of airis maximized. Moreover, the area can be formed so that a suction force Fis maximized by multiplying the total aperture area A of the suctionports 508 by the square of the velocity V of air that passes through thesuction ports 508.

In general, as an expression that expresses the power F of air blow,there is known the following expression (1):Fa=ρ×Q×V/g=ρ33 A×V ² /g  (1)the suction force F can also be similarly expressed by Fa=F, and theformation of the total aperture area of the suction ports 508 isdetermined in correspondence with this.

Describing the representative concrete example of the backup member 506shown in FIG. 63A through FIG. 65B, the backup member 506 shown in FIG.63A and FIG. 63B is adopted by the cleaning method shown in FIG. 62Athrough FIG. 62D, which shows a symmetrical shape type provided with twogrooves 509 located on each of both sides of one suction region 507,producing the same cleaning effect during a reciprocal sliding motion.In this embodiment, by setting the thickness of the cleaning web 505 to0.25 mm, the depth of the groove 509 to 2 mm, groove width to 3 mm, thelength of one suction port 508 to 7 to 8 mm, suction port width to 3 mm,and the travel speed of the cleaning head 521 to 100 mm/sec which isdouble that of the conventional value of 40 to 50 mm/sec, the solderpaste 503 stuck to the lower surface of the screen 504 through onesliding stroke has become nothing, and the amount of solder paste 503staying inside the suction port 508 has become remarkably reduced. It isto be noted that the groove 509 is only required to form a scraping edge505 b at the cleaning web 505, and the edge is preferably at right anglewith respect to the backup surface 506 a. However, the groove edge isnot limited to this, and an inclined surface is acceptable. It hasdiscovered that a similar scraping edge 505 b is formed as shown in thefigure in other portions of the backup member 506 and effectivelyoperating. The shape of the lower portion of the groove 509 is onlyrequired to be the one that does not impede the formation of a pocket511 effective for the cleaning as a consequence of the entry ofthe;cleaning web 505, and the shape thereof is not particularlyspecified.

The backup material 506 of the embodiment shown in FIG. 64 has twosuction regions 507 arranged parallel, and two grooves 509 are providedon each of both sides of the portion where these regions are arrangedparallel and between these two suction regions 507. The cleaning effectis improved further than that of the embodiments of FIG. 63A and FIG.63B by virtue of the increased number of suction regions 507 and grooves509. This embodiment is also the symmetrical type and able to producethe same cleaning effect during the reciprocal sliding.

The backup member 506 of the embodiment shown in FIG. 65A and FIG. 65Bhas two suction regions 507 arranged parallel and is provided with twogrooves 509 located on each of both sides of the portion where theseregions are arranged. The cleaning effect is improved further than thatof the embodiments of FIG. 63A and FIG. 63B by virtue of the increasednumber of suction regions 507. This arrangement is appropriate forremoving the solder paste 503 located on the lower surface of the screen504 and, in particular, more easily removes the printing paste 503 thatis staying and lodging in the holes 501 of the screen 504. Thisembodiment is also the symmetrical type and able to produce the samecleaning effect during the reciprocal sliding.

In short, the present invention is effective when the numbers of thesuction regions 507 and the grooves 509 provided and the order ofarrangement in the sliding direction are set in various combinations.

(Eighth Embodiment)

According to the eighth embodiment shown in FIG. 67A through FIG. 71, asa modification example of the seventh embodiment, as shown in FIG. 67Athrough FIG. 67D, when performing the aforementioned proposed cleaningof the screen 504 by sucking the solder paste 503 that is stuck to thelower surface of the screen 504 or staying in the holes 501 toward thecleaning web 505 side to be adhered and kept to the web 505 through theprocesses of sliding the cleaning web 505 that serves as a wiping memberon the lower surface of the printing screen 504 for supplying the solderpaste 503 that serves as a printing paste on a circuit board that servesas an object to be printed through the holes 501 that serves as aprinting paste supply section of a specified pattern with the cleaningweb 505 backed up by the backup member 506 as shown in FIG. 67A throughFIG. 67D and sucking the solder paste 503 stuck to the lower surface ofthe screen 504 via the cleaning web 505 through the suction port 508provided through the backup member 506 while wiping the solder paste503, the cleaning is performed by continuously sucking the paste bymeans of the plurality of suction ports 508 arranged in the slidingdirection as shown in FIG. 67A through FIG. 69 and FIG. 70A. Theplurality of suction ports 508 may satisfy the same conditions with aninclined arrangement as shown in FIG. 63A and FIG. 63B.

With this arrangement, in cleaning the screen 504 similarly to theaforementioned proposed case, a greater amount of stayed solder paste503 is sucked by repetitively continuously performing the suction by theplurality of suction ports 508, by which a greater amount of paste isaccommodated and kept in the plurality of pockets 511 formed by theentry of the cleaning web 505 into the plurality of suction ports 508.Therefore, the cleaning effect is further improved, and high-qualityprinting can be guaranteed while coping with a further increase in thecleaning speed.

Such a method can be achieved by making use of the aforementionedfeatures of this device merely by using the cleaning device of theprinting screen of the eighth embodiment with the backup member 506replaced by that of the eighth embodiment. In this case, if a pluralityof suction ports 508 are provided in the suction region 507 in thedirection roughly perpendicular to the sliding direction and the suctionports 508 are arranged parallel in the suction region 507 and thesuction area thereof reduces sequentially in the sliding direction asshown in FIG. 67A, FIG. 68, and FIG. 70A, on the backup surface 506 a ofthe backup member 506, then the suction, removal, and accommodation ofthe residual solder paste 503 by the plurality of suction ports 508 areachieved first at a great rate of removal by the suction ports 508 oflarge suction port areas, and subsequently the suction, removal, andaccommodation of the residual solder paste 503 reduced in amount areachieved by the succeeding suction ports 508 whose suction area isreduced without occupying a large space. Then, a cleaning effect higherthan when one suction port continuously cleans the paste can beproduced.

Moreover, if a plurality of suction ports 508 are in proximity to eachother arranged as in the embodiment shown in the figures, then theplurality of suction ports 508 can easily synergetically operate, andthis arrangement is preferable in terms of space saving. Furthermore, byvirtue of the provision of the plurality of suction ports 508 laterallysymmetrically in the sliding direction like the embodiment shown in thefigures, a stable cleaning effect of no difference between the forwardsliding and the reverse sliding can be produced in performing thecleaning in the reciprocal sliding manner. When the suction area isreduced stepwise, the suction ports 508 located on both sides arelarger, and those located inside are smaller as shown in the figures.Therefore, the cleaning is further performed with the suction areaincreased stepwise after the effective cleaning with the suction areasof the aforementioned dimensional relation, and therefore, the cleaningeffect is further increased and stabilized.

The size in the sliding direction of the backup member 506 is restrictedby the dimensional relation to the size of the entire device and thelike. According to one working example, the width w in the slidingdirection of the backup member 506 is 70 mm, the width e of the widesuction ports 508 located on both sides is 10 mm, the width of the threenarrow suction ports 508 is 4 mm, and the proximity interval g of thesuction ports 508 is 4 mm. It is to be noted that the length L of thebackup member 506, which is varied depending on the size of circuitboard that is the object to be printed, is 390 mm according to oneexample.

When a vacuum source is set to a rated flow rate of 1.2 m³/min and arated static pressure of 2000 mmAg on the conditions of this workingexample, FIG. 62A through FIG. 62D and FIG. 71 show the cleaning effectsat various cleaning speeds in cleaning the screen 504 in which the holes501 for mounting the leads of a QFP type semiconductor element of arectangle of about 1 mm×2 mm are arranged which is estimated in terms ofthe retention rate of the solder paste 503 after the cleaning of theholes 501 when the solder paste 503 staying in the entire region of theholes 501 is removed by the cleaning in comparison with the case of thecomparative example that has only one suction port of a width of 10 mm.In the working example, the solder paste 503 had a small residue of afraction of that of the comparative example, and the residue of thesolder paste 503 was able to be suppressed to an amount slightlyexceeding the residue in the case of the comparative example in whichthe printing speed is 100 mm/sec even during a high-speed cleaning of300 mm/sec. The residual rate of the solder paste 503 was calculated onthe assumption that the aperture area of the holes 501 was C, the areaof removal of the solder paste 503 after the cleaning was A, and thearea of residue of the solder paste 503 after the cleaning was B,according to the expression that residual rate (%)=(A/C)×100.

It is to be noted that the three or more suction ports 508 arranged inthe sliding direction may be set so that the widthwise size graduallychanges in the sliding direction, and the style of change may be set ina variety of ways. Furthermore, the preceding suction port 508 can copemore with the high-speed cleaning as the width thereof is greater. Whena suction port 508 of a small width precedes, a sufficient cleaningeffect cannot be obtained, hardly coping with the high-speed printing.Also, in the eighth embodiment shown in FIG. 67A through FIG. 69 andFIG. 70A, it is effective to concurrently use the groove 509 of theembodiment shown in FIG. 62A through FIG. 66, and such a example isshown in FIG. 70B.

As is apparent from the above description according to the presentinvention, in addition to the cleaning effect by suction according tothe previous proposal, by producing the cleaning effects of the printingpaste scraping edge function and the function of accommodating andkeeping the solder paste that has been scraped off in the pocket by thebackup release section, the cleaning effect is further improved, andhigh-performance printing can be guaranteed.

Moreover, in addition to the cleaning effect by suction of the previousproposal, by accommodating and keeping a greater amount of solder pastein the plurality of pockets formed by the entry of the cleaning web intothe suction ports as a result of the plural pockets while sucking anincreased amount of residual solder paste through the repetitivecontinuous suction by the plurality of suction ports, the cleaningeffect can be improved, and high-performance printing can be guaranteedcoping with the further increase in the cleaning speed.

The printing screen cleaning method of the present invention has onefeature that, in cleaning the printing screen by sucking the printingpaste that is stuck to the lower surface of the printing screen andstaying in the printing paste supply section to the wiping member sideto stick and keep the paste by sucking the paste via the wiping memberthrough the suction port provided in the suction region extended in thedirection roughly perpendicular to the sliding direction while wipingthe printing paste stuck to the lower surface of the printing screen bysliding the sheet-shaped wiping member on the lower surface of theprinting screen for supplying the solder paste to the object to beprinted through the printing paste supply section of the specifiedpattern with the wiping member backed up by the backup member, thecleaning is performed by sliding the wiping member on the printingscreen in the state in which the backup of the wiping member ispartially released by the groove parallel to the suction region of thebackup member.

According to the construction described above, in addition to thecleaning of the printing screen similarly to the aforementionedpreviously proposed case in which the printing paste that is stuck tothe lower surface of the printing screen and staying in the printingpaste supply section is stuck and kept by suction to the wiping memberside by wiping the paste by sliding the wiping member on the lowersurface of the printing screen with the wiping member backed up by thebackup member and sucking the paste via the wiping member through thesuction port provided in the suction region extended in the directionroughly perpendicular to the sliding direction, when the portion whichbelongs to the wiping member and in which the backup is partiallyreleased by the groove parallel to the suction region of the backupmember faces the solder paste stuck to the lower surface of the printingscreen, the portion that belongs to the wiping member and is supportedby the opening edge on the rear side in the sliding direction of thegroove in the backup release section operates as the solder pastescraping edge to scrape off the solder paste stuck to the lower surfaceof the printing screen, and while scraping off the backup releasesection retreats inside the groove so as to form a pocket to accommodateand keep the solder paste scraped off. Therefore, the amount of printingpaste removed and carried away from the printing screen by the wipingmember is increased to allow the cleaning effect to be further improved.

In this case, in the state in which the cleaning in the backup releasesection precedes the cleaning by the suction region, there is producedthe synergetic effect that the amount of solder-paste to be accommodatedin the pocket formed by pulling the wiping member into the suction portthrough the cleaning in the suction region is reduced by the amount ofsolder paste removed through the cleaning by the backup release section,and the amount of solder paste that is staying and lodging in theprinting paste supply section and is able to be sucked and accommodatedis increased, for the improvement of the cleaning effect. Moreover, inthe state in which the cleaning by the backup release section succeedsthe cleaning by the suction region, there is produced the synergeticeffect that the cleaning by suction is assisted by scraping and removingthe solder paste, which is accommodated and kept in the pocket formed bypulling the wiping member into the suction port in the cleaning portionby the preceding suction region and left behind on the lower surface ofthe printing screen, through the cleaning by the backup release section,for the improvement of the cleaning effect.

Although it is effective to achieve either one of these two cleaningstates, the cleaning effect is doubled by concurrently using both thecleaning manners. Moreover, it is enabled to cope with them by providingthe cleaning portion by suction and the cleaning portion by the backuprelease section by the required number in repetition in the slidingdirection or providing a plurality of same cleaning portions arranged inaccordance with the need. If two types of cleaning portions are arrangedsymmetrically about the center in the sliding direction, then the samecleaning effect can be obtained by the sliding in either one of theforward and reverse directions, and this arrangement is advantageouswhen performing cleaning by reciprocal sliding.

The above cleaning method can be achieved by a cleaning device of theprinting screen for supplying printing paste onto the object to beprinted through the printing paste supply section of the specifiedpattern and the device being provided with the cleaning head for suckingthe paste via the wiping member through the suction port provided in thesuction region extended in the direction roughly perpendicular to thesliding direction of the backup surface for performing this backup whilesliding the wiping member on the lower surface of the screen with thewiping member backed up by the backup member, and provided with thegroove that is parallel to the suction region and provided on the backupsurface of the backup member and partially releases the backup of thewiping member.

If this device is provided with: the elevation device for pressurizingthe backup member against the printing screen on the cleaning head andreleasing the pressurization; and the movement device for moving thecleaning head into or out of a position under the printing screen fromthe standby position beside the printing screen under the printingscreen and reciprocally moving the head, then the aforementionedoperation of repetitively performing the cleaning and getting ready forthe next printing is executed through the movement under the screenevery time the printing is performed once or every time the printing isperformed a specified number of times or on each required occasion byputting the cleaning head in the standby position so as not to impedethe printing of the printing paste onto the object to be printed by theprinting screen in the screen printing apparatus, enabling the stableperformance of high-accuracy printing to be guaranteed for a long term.

Furthermore, if the above-mentioned device is provided with the supplysection for feeding and supplying the wiping member and the unwindingsection for unwinding the wiping member, then the cleaning can beperformed with a new wiping member every time by unwinding the wipingmember by the unwinding section in accordance with the feed and supplyof the wiping member from the supply section every time the cleaningends once, enabling the aforementioned characteristic cleaning functionto be stably maintained.

If the suction ports are arranged in an array in the direction roughlyperpendicular to the sliding direction in each device, the suction forceis increased by reducing the size of individual suction port to increasethe suction efficiency while securing the required amount of totalsuction air in terms of the total opening area, and the cleaningfunction by suction can be improved.

The aforementioned method and device employs the backup member, which isprovided with the backup surface for backing up the wiping member tobring the member in contact with the printing screen, the suction regionthat has the suction port on the backup surface and is provided in thedirection roughly perpendicular to the sliding direction, and the grooveextended parallel to this suction region.

As concrete representative examples, there are enumerated the backupmember characterized by the provision of the backup surface for backingup the wiping member to make the member slide on the printing screen,the suction region that has the suction port on the backup surface andis provided in the direction roughly perpendicular to the slidingdirection and one or a plurality of grooves that are provided on oneside of this suction region and extended parallel to the suction region;

the backup member characterized by the provision of the backup surfacefor backing up the wiping member to make the member slide on theprinting screen, the suction region that has the suction port on thebackup surface and is provided in the direction roughly perpendicular tothe sliding direction, and one or a plurality of grooves that areprovided on each of both sides of this suction region and extendedparallel to the suction region;

the backup member characterized by the provision of the backup surfacefor backing up the wiping member to make the member slide on theprinting screen, the two suction regions that have the suction port onthe backup surface and are provided in the direction roughlyperpendicular to the sliding direction and one or a plurality of groovesthat are provided on each of both sides of the portion where these twosuction regions are extended and arranged parallel to the suctionregions; and

the backup member characterized by the provision of the backup surfacefor backing up the wiping member to make the member slide on theprinting screen, the two suction regions that have the suction port onthe backup surface and is provided in the direction roughlyperpendicular to the sliding direction and one or a plurality of groovesthat are provided in positions located adjacently on each of both sidesof the portion where these two suction regions are arranged, providedbetween the two suction regions and arranged parallel to the suctionregions.

The above-mentioned members are each suitable in terms of the suctionefficiency since the suction ports are provided in an array in thedirection perpendicular to the sliding direction.

The printing screen cleaning method of the present invention has anotherfeature that, based on a printing screen cleaning method for cleaningthe printing screen by sucking the printing paste that is stuck to thelower surface of the printing screen and staying in the printing pastesupply section to the wiping member side to stick and keep the paste bysucking the paste via the wiping member through the suction portprovided for the backup member while wiping the printing paste stuck tothe lower surface by sliding the wiping member on the lower surface ofthe printing screen for supplying the solder paste to the object to beprinted through the printing paste supply section of the specifiedpattern with the wiping member backed up by the backup member, thecleaning is performed by continuously sucking the paste by the suctionports arranged parallel in the sliding direction.

According to the construction described above, in the cleaning of theprinting screen similarly to the aforementioned previously proposed casein which the printing paste that is stuck to the lower surface of theprinting screen and staying in the printing paste supply section isstuck and kept by suction to the wiping member side by wiping the pasteby sliding the wiping member on the lower surface of the printing screenwith the wiping member backed up by the backup member and sucking thepaste via the wiping member through the suction port provided in thedirection roughly perpendicular to the sliding direction, byaccommodating and keeping a greater amount of solder paste in theplurality of pocket portions formed by the entry of the wiping memberinto the suction ports as a result of the plural pocket portions whilesucking an increased amount of residual solder paste through therepetitive continuous suction by the plurality of suction ports as aresult of the repetition, the cleaning effect can be improved, andhigh-performance printing can be guaranteed coping with the furtherincrease in the cleaning speed.

As a printing screen cleaning device for achieving this method, it issufficient to provide a device provided with the cleaning head forsupplying the printing paste onto the object to be printed through theprinting paste supply section of the specified pattern and sucking thepaste via the wiping member through the suction port provided on thebackup surface for performing the backup while sliding the wiping memberon the lower surface of the printing screen with the wiping memberbacked up by the backup member, the backup surface having a plurality ofsuction ports arranged side by side in the sliding direction, and theplurality of suction ports performing continuous suction.

In this case, if a plurality of suction ports are provided in thesuction region in the direction roughly perpendicular to the slidingdirection and the suction ports, which are arranged parallel to thesuction region and the suction area of which reduces stepwise on thebackup surface of the backup member, then the suction, removal, andaccommodation of the residual solder paste by is the plurality ofsuction ports are achieved first at a great rate of removal by thesuction ports of large suction port areas, and subsequently the suction,removal, and accommodation of the residual solder paste reduced inamount are achieved by the succeeding suction ports whose suction areais reduced without occupying a large space. Then, a higher cleaningeffect can be produced.

The plurality of suction ports easily synergetically operate since theplurality of suction ports are arranged in proximity to each other, andthis arrangement is suitable in terms of space saving.

If a plurality of suction ports are provided laterally symmetrically inthe sliding direction, a stable cleaning effect of no difference betweenthe forward sliding and the reverse sliding can be produced inperforming the cleaning in the reciprocal sliding manner. When thesuction area is reduced stepwise, the suction ports located on bothsides are larger, and those located inside are smaller. Therefore, thecleaning is further performed with the suction area increased stepwiseafter the effective cleaning with the suction areas of theaforementioned dimensional relation, and therefore, the cleaning effectis further increased and stabilized.

For the wiping member backup member used for the aforementioned onemethod and the device for materializing the method, there is employedone constructed of the backup surface for backing up the wiping memberand sliding the member on the printing screen and the suction regionprovided with the suction ports on this backup surface in the directionroughly perpendicular to the sliding direction, the plurality of suctionports being arranged parallel to the suction region and arranged side byside in the sliding direction.

As the representative examples of the member, there are enumerated thewiping member backup member of which the plurality of suction ports havesuction areas reducing stepwise in the sliding direction;

the wiping member backup member of which the plurality of suction portsare arranged in proximity to each other; and

the wiping member backup member of which the plurality of suction portsare arranged laterally symmetrically in the sliding direction.

By appropriately combining arbitrary embodiments of the aforementionedvarious embodiments, the effects owned by each of the embodiments can beproduced.

It is to be noted that the sixth through eighth embodiments can also beapplied to the solder paste printing method and apparatus that has thepressurizing member of the first through fifth embodiments and to asolder paste printing method and apparatus that has no pressurizingmember.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

1. A solder paste printing apparatus for printing a solder pastesupplied onto a surface of a printing mask having a number of opening,the printing apparatus comprising: a squeegee movable in a printingdirection along the surface of the printing mask for printing on acircuit-forming body placed on a back surface of the printing mask; andan elongated pressurizing member that has an axial direction extendingroughly parallel to an axial direction of the squeegee, the pressurizingmember being arranged to form between the pressurizing member and theprinting mask a first gap through which the solder paste can pass in adirection opposite to the printing direction of the squeegee during asolder paste printing operation, the pressurizing member also beingarranged to form between the pressurizing member and the squeegee asecond gap through which the solder paste can pass from the first gaptoward the squeegee side of the pressurizing member, wherein thepressurizing member is provided in a vicinity of an edge of the squeegeeso that a pressure toward the printing mask is applied to the solderpaste by the pressurizing member when the solder paste passes throughthe first gap located between the pressurizing member and the printingmask during the solder paste printing operation, wherein across-sectional shape of the pressurizing member that is perpendicularto the axial direction of the pressurizing member is varied in the axialdirection of the pressurizing member according to the number and size ofthe openings of the printing mask, thus varying the pressure to beapplied from the pressurizing member to the solder paste against theprinting mask.
 2. A solder paste printing apparatus as claimed in claim1, wherein the pressurizing member is movably mounted with respect tothe squeegee between a pressurizing position where the pressure isapplied to the solder paste and a retreated position where the applyingof the pressure is released, provided with an axial direction extendedroughly parallel to the axial direction of the squeegee in thepressurizing position, is able to form the first gap through which thesolder paste can pass in the direction opposite to the printingdirection of the squeegee during the solder paste printing, and isarranged so that the second gap through which the solder paste can passfrom the first gap toward the squeegee side is arranged between thepressurizing member and the squeegee.
 3. A solder paste printingapparatus as claimed in claim 1, wherein the pressurizing member is around bar.
 4. A solder paste printing apparatus as claimed in claim 1,wherein a pair of squeegees are provided, and at least one of the pairof squeegees is consistently brought in contact with the printing maskat least during printing.
 5. A solder paste printing apparatus asclaimed in claim 1, wherein the first gap has a roughly wedge-shapedcross-section shape that is narrowed toward the squeegee.
 6. A solderpaste printing apparatus as claimed in claim 1, wherein the pressurizingmember has a height from the surface of the printing mask, the heightbeing lower than a rolling height of the solder paste during printing,and the pressurizing member sinks in the rolling solder paste during theprinting.
 7. A solder paste printing apparatus as claimed in claim 1,wherein the pressurizing member is fixed so as to be unable to rotate.8. A solder paste printing apparatus for printing a solder pastesupplied onto a surface of a printing mask having a number of openings,the printing apparatus comprising: a squeegee movable in a printingdirection along the surface of the printing mask for printing on acircuit-forming body placed on a back surface of the printing mask; andan elongated pressurizing member that has an axial direction extendingroughly parallel to an axial direction of the squeegee the pressurizingmember being arranged to form between the pressurizing member and theprinting mask a first gap through which the solder paste can pass in adirection opposite to the printing direction of the squeegee during asolder paste printing operation the pressurizing member also beingarranged to form between the pressurizing member and the squeegee asecond gap through which the solder paste can pass from the first gaptoward the squeegee side of the pressurizing member, wherein thepressurizing member is provided in a vicinity of an edge of the squeegeeso that a pressure toward the printing mask is applied to the solderpaste by the pressurizing member when the solder paste passes throughthe first gap located between the pressurizing member and the printingmask during the solder paste printing operation, wherein thepressurizing member is rotatable in a direction reverse to a rollingdirection of the solder paste around the pressurizing member duringprinting.
 9. A solder paste printing method for printing a solder pastelocated on a surface of a printing mask having at least one opening, theprinting method comprising: moving a squeegee on the surface of theprinting mask in a printing direction so as to print on acircuit-forming body placed on a back surface of the printing mask viathe opening; applying a pressure toward the printing mask from anelongated pressurizing member to the solder paste by making the solderpaste pass in a direction opposite to the printing direction of thesqueegee through a first gap formed between the printing mask and thepressurizing member during solder paste printing in a state in which thepressurizing member provided in a vicinity of an edge of the squeegee ispositioned in a pressurizing position where a pressure is applied to thesolder paste from a retreated position where no pressure is appliedthereto; and making the solder paste pass again through the first gaplocated between the pressurizing member and the printing mask after thesolder paste that is passing from the first gap toward the squeegee sideof the pressurizing member passes through a second gap located betweenthe squeegee and the pressurizing member, wherein a cross-sectionalshape perpendicular to the axial direction of the pressurizing member isvaried in the axial direction of the pressurizing member according tothe number and size of the openings of the printing mask, thus varyingthe pressure to be applied from the pressurizing member to the solderpaste against the printing mask.
 10. A solder paste printing method asclaimed in claim 9, wherein an interval of the first gap is smaller thana rolling height of the solder paste during printing, and thepressurizing member sinks in the rolling solder paste during printing.11. A solder paste printing method as claimed in claim 9, wherein thepressurizing member is fixed so as to be unable to rotate.
 12. A solderpaste printing method for printing a solder paste located on a surfaceof a printing mask having at least one opening, the printing methodcomprising: moving a squeegee on the surface of the printing mask in aprinting direction so as to print on a circuit-forming body placed on aback surface of the printing mask via the opening; applying a pressuretoward the printing mask from an elongated pressurizing member to thesolder paste by making the solder paste pass in a direction opposite tothe printing direction of the squeegee through a first gap formedbetween the printing mask and the pressurizing member during solderpaste printing in a state in which the pressurizing member provided in avicinity of an edge of the squeegee is positioned in a pressurizingposition where a pressure is applied to the solder paste from aretreated position where no pressure is applied thereto; and making thesolder paste pass again through the first gap located between thepressuring member and the printing mask after the solder paste that ispassing from the first gap toward the squeegee side of the pressurizingmember passes through a second gap located between the squeegee and thepressurizing member, wherein the pressurizing member is rotated in adirection reverse to a rolling direction of the solder paste around thepressurizing member during printing.
 13. A solder paste printingapparatus for printing a solder paste supplied onto a surface of aprinting mask having at least one opening, the printing apparatuscomprising: a squeegee movable in a printing direction along the surfaceof the printing mask for printing on a circuit-forming body placed on aback surface of the printing mask; an elongated pressurizing member thathas an axial direction extending roughly parallel to an axial directionof the squeegee the pressurizing member being arranged to form betweenthe pressurizing member and the printing mask a first gap through whichthe solder paste can pass in a direction opposite to the printingdirection of the squeegee during a solder paste printing operation thepressurizing member also being arranged to form between the pressurizingmember and the squeegee a second gap through which the solder paste canpass from the first gap toward the squeegee side of the pressurizingmember, wherein the pressurizing member is provided in a vicinity of anedge of the squeegee so that a pressure toward the printing mask isapplied to the solder paste by the pressurizing member when the solderpaste passes through the first gap located between the pressurizingmember and the printing mask during the solder paste printing operation;a pressure sensor that is provided within a range of printing on theback surface of the printing mask, which is a range in which thesqueegee moves and detects a pressure of the solder paste applied via apressure detection opening formed on the printing mask; and a controlmeans for controlling driving conditions of the squeegee incorrespondence with a detection result of the pressure sensor.
 14. Asolder paste printing apparatus as claimed in claim 13, wherein thecontrol means executes control on a basis of a pressure waveform thatrepresents a change with a lapse of time of the pressure of the solderpaste detected by the pressure sensor.
 15. A solder paste printingapparatus as claimed in claim 13, wherein the control means is providedwith a database in which a pressure waveform of the solder paste isregistered and controls the driving conditions of the squeegee bycomparing the pressure waveform detected by the pressure sensor with thesolder paste pressure waveform that is registered in the database andbecomes a criterion of decision.
 16. A solder paste printing apparatusas claimed in claim 13, wherein a squeegee up-and-down drive device forchanging a relative position in the vertical direction of the squeegeewith respect to the printing mask is provided, and the relative positionis adjusted by driving the squeegee up-and-down drive device by thecontrol means.
 17. A solder paste printing apparatus as claimed in claim13, wherein a printing drive device for moving the squeegee in theprinting direction is provided, and a travel speed in the printingdirection of the squeegee is adjusted by driving the printing drivedevice by the control means.
 18. A solder paste printing apparatus asclaimed in claim 13, wherein a pressurizing member horizontal movementmechanism for changing a relative position of the pressurizing memberwith respect to the squeegee is provided, and the relative position ofthe pressurizing member is adjusted by driving the pressurizing memberhorizontal movement mechanism by the control means.
 19. A solder pasteprinting apparatus as claimed in claim 13, wherein a pressurizing membervertical movement mechanism for changing a relative position of thepressurizing member with respect to the printing mask is provided, andthe relative position of the pressurizing member is adjusted by drivingthe pressurizing member vertical movement mechanism by the controlmeans.
 20. A solder paste printing apparatus as claimed in claim 13,wherein the pressure sensor is provided short of a printing start end ofthe circuit-forming body, and the pressure detection of the solder pasteis performed before starting the printing of the circuit-forming body.21. A solder paste printing method for printing a solder paste locatedon a surface of a printing mask having at least one opening the printingmethod comprising: moving a squeegee on the surface of the printing maskin a printing direction so as to print on a circuit-forming body placedon a back surface of the printing mask via the opening; applying apressure toward the printing mask from an elongated pressurizing memberto the solder paste by making the solder paste pass in a directionopposite to the printing direction of the squeegee through a first gapformed between the printing mask and the pressurizing member duringsolder paste printing in a state in which the pressurizing memberprovided in a vicinity of an edge of the squeegee is positioned in apressurizing position where a pressure is applied to the solder pastefrom a retreated position where no pressure is applied thereto; andmaking the solder paste pass again through the first gap located betweenthe pressurizing member and the printing mask after the solder pastethat is passing from the first gap toward the squeegee side of thepressurizing member passes through a second gap located between thesqueegee and the pressurizing member, wherein the pressure of the solderpaste flowing between the pressurizing member and the printing mask isincreased by the pressurizing member provided in a vicinity of the edgeportion of the squeegee, and the driving conditions of the squeegee arecontrolled by detecting the increased pressure of the solder paste andcomparing the detected pressure with a specified pressure preparatorilyregistered.
 22. A solder paste printing method as claimed in claim 21,wherein the pressure of the solder paste is measured before startingpattern printing of the circuit-forming body, and the control of thedriving conditions of the squeegee is completed before starting thepattern printing.